Unused Puzzle Types

While gathering puzzle types and their synonyms to add to indexed puzzles, I also encountered a number of puzzle types which are not represented in the index:

Crossword-type puzzles:

• Boomerangs: 6-letter words are entered on curved paths bowing to the left and the right. Except for the words at the ends, each word shares two letters with each of three words entered the other direction.
  
• Brick by Brick: A diagramless 15x15 crossword with an entry reading all the way across the middle row, with normal cluing. Additionally, the solution (excluding the middle entry, but including black squares) is broken up into 3x2 blocks which are provided in scrambled order.
• Bricks and Mortar, Brick by Brick (again), or Super Sixes: A grid is given, divided by heavy bars into 2x4 sections. Numbered clues provide 8-letter answers to be entered starting at correspondingly numbered cells and proceeding in a direction for you to figure out around the brick. Adjacent letters across a heavy bar are identical. The Super Sixes version uses 6-letter answers and 2x3 bricks.
  
• Color Wheels: A grid of triangles is given, with hexagonal holes between lines where you enter words. Three different colors of arrows mark where to enter words, one for words reading across, one for words reading diagonally upward, and one for words reading diagonally downward.
  
• Diamond Rings: This puzzle features diamond-shaped spaces with a lattice of circles placed so as to occupy one or two opposite vertices of each diamond. The circles are numbered, and the answers to corresponding 5-letter clues are entered in a circle and its 4 adjoining diagrams, with the letters in no particular order.
• 5-Star Stumper: There are five pentagrams. Each is surrounded by 10 pentagonal spaces for letters, five between the arms of the star and 5 at the vertices. These are arranged in a loop so that one pentagon is shared by each pair of nearest stars. Two clues are give for words to enter around each star, with the starting cell and direction for each pair of words indicated by a number and arrow. In addition, the pentagons along the outer edge of the figure are shaded. A second set of clues is given for a sequence of words to be entered in this shaded path, clockwise, but starting at a point for you to determine. The unshaded cells in the interior spell a final message, row by row.
  
• Hedgehogs and Worms: A grid is divided into 3x3 sections. The center square of each section is numbered, and an arrow points out of it into one of the 8 surrounding squares. Clues are given for the 9-letter hedgehog words which start in their correspondingly numbered squares, follow the arrow, and then continue clockwise or counterclockwise as indicated by a + or - after the clue. The sequence of worm words is clued in order, and are entered all the way across the rows of the grid which do not have the numbered squares, sometimes wrapping around from the end of one row to the start of the next. Letters in numbered squares provide a final answer.
• Helter Skelter: Words read in 8 directions which are given implicitly in the grid, because each word starts at its number and passes through the next number sequentially. The last word's direction is not given.
• Lucky Sevens: A grid is given made of seven heavily outlined 7-shapes (three squares across and five down) nested under one another. Labeled clues are given for the seven-letter words to be entered in each seven-shape and for each row of varying length, including the single letter at the bottom.
  
• Moving Staircases: A square grid (typically 7x7) has the main top-left-to-bottom-right diagonal as black squares. Two sets of clues are given, not in grid order: "Short" answers go straigfht across a row, skipping the black square. "Long" answers climb up when they get to the black square, using the start of one short answer and the end of another.
• Pencil Pointers, also called Arrow Routes: This is a standard crossword format in Scandinavian countries, imported for use in English. The grid cells are oversized, and terse clues are written into the gray (what would usually be black) cells. In some cases a gray cell is divided to hold two very short clues. Arrows next to the clues indicate where to enter the words. There is no symmetry and there may be a few isolated unchecked letters (including in the first row and column, with arrows stretching from adjacent gray cells providing the clues for the words starting there).
  
• Pent Words: Clues are given for (usually two) words to be entered consecutively in each row. Clues are also given for 5-letter pentomino words, which are entered into nonoverlapping pentominoes you have to determine in the grid. The pentomino words are entered row by row in their pentominoes, even if this means a word skips over a gap in a U-shaped pentomino.
• Quadruple Cross: The grid consists of some rows and columns of squares, two rows/columns apart so that there are 2x2 holes in the interior. The intersections are numbered, and clues for two 5-letter words are provided at each number, but you have to figure out which one goes across and which goes down by matching with answers at other intersections.
• Retrograde Battleships: Shade in the fleet in the grid, so that no two ships touch, even diagonally, but instead of the normal numeric Battleships clues, the grid is filled with possible ship placements and you can only shade whole ships among them.
• Section Eight: A round grid with 8 rings is divided into 8 sectors. The innermost ring has one letter in each sector, the next ring out two, and so on to eight letters per sector in the outermost ring. Clues are provided for one word per every eight letters in each of the rings, though the answers may vary in length. In the outermost ring you are given the starting spaces for all the words and hence their lengths. Elsewhere you have to determine the starting spaces and the direction the words go, which can be different for each ring. In each sector, the letters in each ring are a transdeletion of the letters in the next outer ring in the same sector, though these letters are usually parts of one to three words and not a whole clued word. There is also a Section Six version of this puzzle which uses 6 of everything the Section Eight version has 8 of.
  
• Slot Machine: Clues are given for words entered across each row. Clues are also given for words reading down each column, but the column words may start anywhere in the column and wrap around.
• Snake Charmer: Words are entered consecutively along a long loop (which is presented in an S shape to resemble a snake). The words go twice around the loop, entered consecutively but overlapping words from the other pass. Answer locations are numbered in order (so there are two interleaved sequences of increasing numbers around the loop).
• Sunburst: A round grid has a single circle at the center and 4 rings around it with the same number of cells in each ring. Two sets of clues are given, short words and long words. The long words are entered in the grid and all end with the same single letter at the center. The short words are transdeletions of the long word. The outermost ring is numbered and the short words are numbered to match; the long clues are not numbered.
  
• Touchword: Clues are given for answers to be entered consecutively in each row. There are no actual crossings, but each letter must match either the one above it or the one below it or both, wrapping around from the bottom to the top of the grid.
• Triangle Tangle: A zigzagging grid of right triangles is given. The 4 letter answers alternately read straight down and diagonally up and right, so that each "up" word is a reversal of the last two letters of one down answer plus a reversal of the first two letters of another. The puzzle type Back and Forth (which is in the index) is similar but with three-letter halves instead of 2.
  
• Zigzagnut: A grid of squares is given, divided by heavy borders into paths which alternate steps across and down. These regions are numbered and provided with a clue for each. There are also clues for two words reading across each row which are given in order but you are not told which row each pair of clues goes with.
  

Other word puzzles:

• Alphablocks: The alphabet is printed in a column with spaces on both sides. 52 trigrams are given in alphabetical order. Add one trigram on each side of each letter to form 26 7-letter words.
  
• Anagram Magic Square: 25 numbered clues are given. An oversized 5x5 grid contains a word in each cell, but the clue answers are transadditions of each given word. The cells are not numbered; instead, you add the numbers to the cells as you solve; these numbers will form a magic square when the puzzle is complete, and the extra letters spell a final message in grid order.
• Card Quote, also called Deck it Out: A blank 13x4 grid representing a deck of cards is provided. 13 words are clued, one for each rank, with blanks for the typically 6-letter answers and suit symbols under 4 of the blanks for each answer to be transferred into the deck in the manner of a double crostic. The deck spells out a final message.
• Chess Words: A chessboard is given with letters on each square and the pieces that normally start in rank 1 pictured below the board. You are to form 8 8-letter words starting with the letters on their starting spaces, moving as those pieces move (so the knight makes a partial knight's tour, the king has to go one space at a time, etc.)
  
• Code crosswords, also called Codewords: A cryptogram in the form of a block-style crossword. Where the clue numbers would go are instead cipher numbers in every square. The puzzle is usually a pangram; every letter appears at least once.
• Coined Phrases: Somewhat like the lettered dice puzzle in the index, but it uses five coins with naturally just two letters on each one. Clues are provided for some words that can be formed with the letters on the coins, using all the letters at least once. Once you figure out which letters are on each coin, you are to arrange them in some order so that another unclued word can be formed, and if you flip all the coins over but leave them in the same order, yet another unclued word is formed.
• Crack It On: Fill a letter into each region so the given words are spelled out by the letters in each row and each column. However, some of the regions are larger than a single cell and count as being in each row and column they cross.
  
• Family Reunions: Find sets of 10 words with a common theme. A transdeletion of each word is provided.
• Letter Pairs: Place letters in some cells of the grid so the given words are spelled out horizontally and vertically. Words do not intersect; each letter placed in the grid is used in exactly one of the given words. A black dot is given on the border between every pair of cells that contain the same letter in the solution.
  
• Letters from Outside: A 5x5 block-style crossword grid is given, to be filled with letters given outside the grid, one or two for each row, column, and main diagonal, similar to Slide Show.
  
• Overstuffed Sandwiches: Words are provided with one letter missing, but each word has at least two letters which can complete it. The space for the missing letter is divided in two diagonally. Correctly filled, the letters above the diagonal across all the words spell one additional word, and the letters below the diagonal spell another, usually forming a phrase.
• Slide Show: A 5x4 grid is given with two letters already entered. The other letters surround the grid, with two outside letters to slide somewhere into each row and two into each column to create a word rectangle.
  
• Syllabism, also called Syllable Saying: Clues are given for longish (typically 8-12 letter) words. The answers are broken up into syllables and all the syllables for all answers are provided in a single alphabetized list.
• Word Rummy, also called 500 Rummy: A 13x4 grid is provided already filled in with letters, with row and column labels to represent a deck of cards. You are to form 7-letter words which combine a set of 3 or 4 cards of the same rank (in any suit order) and a run of 3 or 4 consecutive cards in the same suit (used in order in the word). The set and run for a word may not reuse the same card, though the cards are reused in other words. The set and run letters may not be interleaved in the word, but either the set or the run may come first. This puzzle doesn't have any definite answer; you are just challenged to form all the words you can.

Nikoli-style puzzles. There are a LOT of these. I've divided the list into three parts. First, there are these classic types, ones that have been around a long time, used in USPC, puzzle magazines, Grandmaster Puzzles, or other sources where a lot of people have seen them.

• Aqre: Shade some cells which form a single orthogonally connected group. Regions with numbers must have that many shaded cells. There cannot be four consecutive shaded cells in any row or column.
  
• Araf, or Aidabeya: A grid contains various numbers. Divide it into regions each containing two numbers so that the area of each region is strictly between (not inclusive) those numbers. In one variation not given a specific name, numbers can be preceded by less-than or greater-than signs to indicate the area must be on one side of one of the given numbers.
  
• Arrows: A grid is given with a number in each cell. Outside the grid there is an empty cell at each end of each row and column in which you must draw an orthogonal or diagonal arrow pointing into the grid (so only 2 or 3 choices at each place). Each number in the grid must be pointed to by exactly that many arrows.
• Blokus: Inspired by the board game, shade in shapes in the grid matching the ones given. These shapes cannot touch along an edge. Intersections in the grid with a dot must have two of the shapes meet at a corner there; shapes cannot meet at a corner elsewhere.
  
• Castle Wall: Draw a single closed loop from orthogonal connections of empty cells in the grid. Not all cells need be used. Black cells must be outside the loop, while white cells with heavy outlines must be inside it, and gray cells can be inside or out. Numbers with arrows (on cells of either color) specify the number of segments of the loop (connections between cells, not the cells themselves) which lie along the direction indicated by the arrow.
• Choco Banana: A grid is given with numbers in some cells. Shade some cells so that the groups of connected shaded cells are always rectangular or square, and so that the groups of connected unshaded cells never are. Each number tells the area of the group it is in, though the group may be shaded or unshaded.
  
• Clouds, Rain Clouds, or Radar: A grid is given with numbers for each row and column telling how many cells have clouds. There may also be clues indicating the presence of cloud sections or the absence of them. Clouds are rectangles (in some versions with rounded corners where segments are given in the grid, similar to Battleships clues) with width and height at least 2, and they never touch, not even diagonally.
• Compass: A grid contains clues in some cells with an X shape and numbers in some of the spaces between arms of the Xs. Divide the grid into regions along ithe grid lines so that exactly one clue is in each region. A number on the top side of an X tells how many of the cells in the region are north of the clue (regardless of their east-west position), and so on for the other sides.
• Coral: Shade an orthogonally connected set of cells. No 2x2 region can be completely shaded, and all unshaded cells must be in orthogonally connected groups touching the edge of the grid. Clues give the sizes of groups of shaded cells in the row or column in order, as in Paint by Numbers.
  
• Cross the Streams: A combination of Nonograms and Nurikabe. Shade some cells in the grid. The numbers outside the grid are standard Nonograms clues, but ? indicates a group of unknown size, and * indicates an unknown number of groups of any sizes, possibly none. All the shaded cells must be connected orthogonally into a single group, and no 2x2 region can be completely shaded.
• Digital Battleships, or Sum Battleships: Circle the fleet in the grid, as in standard Battleships puzzles with no two ships touching, even diagonally. But each cell in the grid has a number, and the clues outside the grid tell the sum of the numbers on ship segments in the grid.
• Double Choco: A provided grid has half its cells already shaded gray. Divide the grid into regions, each of which can be split into a gray polyomino and a white polyomino which are congruent (but may be rotated or reflected). If a region contains one or more of the given numbers, each such number tells the area of either like-colored half of the region.
  
• Double Minesweeper: Like regular minesweeper, but empty cells may contain 0, 1, or 2 mines.
• Eminent Domain, or Four Winds: A grid is given with numbers in some cells. You must draw horizontal and/or vertical lines from each number so that each empty cell is on exactly one line and each number is connected by lines to that many other cells (besides itself). Lines cannot span two numbers, nor can there be lines not connected to a number. Hukuwall is a cryptic version of this puzzle, where each number is consistently replaced by the same letter. Four Winds with Parks is a version where one cell in each row and column must remain empty. On a hex grid this puzzle may be called Six Winds.
  
• Hamle: A grid is given with some numbered cells. Each cell should move in one of the orthogonal directions the number of spaces as its number. The paths can cross in this puzzle, but when the moves are done, the moved cells should not be orthogonally adjacent and the empty cells should all be orthogonally connected.
  
• Hebi-Ichigo: Place numbers in some of the empty cells so they form snakes 5 units long consisting of the numbers 1 to 5 in order, orthogonally connected. Snakes can touch other snakes only diagonally. Each snake's 1 cell is its head, and it is looking in the direction opposite its 2 cell, up to the next shaded cell or the edge of the grid. No other snake parts are allowed to appear in this space. The clues written on shaded cells indicate which numbered snake part is the first one encountered in the direction indicated by the arrow, and before another black cell. If the clue is a 0, if means there is no snake in that space.
  
• Hidato: A numbered path puzzle like the Snake, but all cells are used (no adjacency rule) and diagonal moves are permitted (including crossing over your path diagonally). Compare with Numbrix, which doesn't allow the diagonals. In Rook Hidato rook moves are allowed, and U-turns prohibited, making it a bit of a cross between Hiroimono and Hidato. Number Snake is another name for this puzzle, with versions allowing and disallowing diagonal connections.
  
• Hiroimono, or Goishi Hiroi: This is a classical Japanese variation of peg solitaire. Stones are arranged at lattice points. You have to figure out how to remove all the stones, starting at any stone, and proceeding to other stones along lattice lines, and never U-turning; you can go straight or turn left or right to the nearest stone after picking up each stone.
  
• Hundred, or C Notes: A grid is given with a digit in every cell. Place a second digit in some cells (before or after the given digit) to form two-digit numbers so that the sum of each row and column is 100.
• Icebarn: Draw a path of orthogonal connections between cells that connects the given entrance and exit arrows. The path must go through each arrow connecting two cells in the direction of the arrow. Groups of shaded cells with heavy outlines are ice patches. The path must go through each ice patch at least once. The path cannot turn within an ice patch. The path can cross itself only within an ice patch.
  
• Inverse LITSO: This is actually the inverse of LITS, not LITSO, but the inversion allows O tetrominoes to appear. Shade four cells in each given region to form a tetromino. Tetrominoes of the same shape may not share an edge. All the unshaded cells must be connected along their edges, and no 2x2 area may be entirely unshaded.
  
• Japanese Sums: Shade some cells in the grid and place numbers in the indicated range in all other cells. Numbers cannot repeat in a row or column, but not all numbers will be used in every row or column. The numbers outside the grid give the sums of adjacent groups of numbers in that row or column, in order.
  
• Japanese Sums and Loop: Like Japanese Sums, but the cells without numbers must be able to be connected in a single loop of orthogonal connections between cells.
  
• Kanaore: Place one letter in each cell. Each word given below the grid can be found in the grid, starting at the correspondingly numbered cell and making the first step in the direction given by the arrow next to the word, and making subsequent steps in any orthogonal direction, witout reusing the same cell in the same word. The same cell may be used in different words.
  
• Kin-Kon-Kan: Place one diagonal mirror in a cell of each region so that like letter-number pairs outside the grid are connected by orthogonal light beams reflecting off these mirrors, and the number indicates how many mirrors the beam hits. Each mirror must be hit by at least one beam.
• Konarupu, or Corner Loop: Draw a single closed loop of orthogonal connections among the given dots. The numbers in some cells tell how many times the loop makes a 90-degree turn at the cell's corners.
  
• Kropki: A Latin square puzzle in which a white dot appears over each boundary between two consecutive numbers, and a black dot if one number is double the other. All possible dots are given, but the dot between 1 and 2 can be either color.
• Kurotto: A grid is provided with circles in some cells, and numbers in some circles. Shade some empty cells (cells with circles cannot be shaded). The black cells are divided into orthogonally connected groups. Each number in a circle indicates the total area of the black cell groups which share an edge with it.
• Liar Diagonal Slitherlink: Draw a loop as in regular Slitherlink, but once per row and once per column, the loop goes diagonally across a cell. The numbers in those cells are "liars" in that they do not indicate the correct number of the cell edges that are part of the loop.
  
• Lighthouses: The numbers on black cells in the grid represent lighthouses, which shine on all the squares in its row and column, including through other ships or lighthouses. The number on each lighthouse represents the number of ships it illuminates. You are to locate all the single-cell ships, which do not touch other ships or lighthouses, even diagonally.
• Lighthouse Battleships: A combination of Lighthouses with Battleships. The ships are now a given Battleships fleet rather than all occupying single cells, and the numbers are lighthouse clues telling the number of illuminated segments.
• Minesweeper Battleships: Locate the given fleet of ships in the grid, which cannot touch, even diagonally, as in standard Battleships puzzles. Clue numbers in the grid are never part of ships and indicate the number of ship segments in the 8 adjacent cells.
• Mochikoro: A grid containing numbers in some cells. Like Nurikabe, you are to shade in some of the empty cells to leave each number in a separate "island" of cells the size of that number, and also like Nurikabe, you can't shade all of a 2x2 region. But there can be unnumbered islands in this puzzle, and instead of the black cells all having to be connected, in this puzzle all the white islands have to be diagonally connected.
• Myopia: Draw a single nonintersecting loop along the cell boundaries. Some cells have one or more arrows in them; these arrows indicate the closest direction(s) to that cell that the loop edge comes. If multiple directions are tied for closest, there will be multiple arrows. Myopia can be combined with many other loop and binary-determination puzzle types as a variant type of clue.
  
• Nanro, or Number Road: A grid is provided, divided into heavily outlined regions and with numbers in some cells. Add numbers to other cells so that each region has at least one number, the numbers within each region are all the same. The value of the numbers in each region must equal the number of numbers in the region. All the numbered cells must form a single orthogonally connected region. When numbers are adjacent across a region boundary they must be different numbers, and nowhere are there numbers in all cells of a 2x2 region. In the Nanro (Signpost) variant, the given numbers are small ones in the top left corner of cells. These don't count as numbered cells, but they force the regions they are in to use that number.
  
• Norinori: A grid is divided into heavily outlined regions. Shade in some cells so that every region contains exactly two shaded cells, and each shaded cell is orthogonally adjacent to exactly one other (possibly from a different region).
• Number Cross: A grid is provided with numbers in every cell and one number outside each row or column. Shade some of the cells so the numbers outside the grid give the sum of the unshaded numbers in their row or column.
  
• Numbrix: A numbered path puzzle like the Snake, but all cells are used (no adjacency rule). Compare with Hidato, which allows diagonal moves.
• Number Parades: A grid divided into regions is provided. Put numbers into some reasons so that the numbers in each region are consecutive starting from 1 when read in usual reading order row by row top to bottom, left to right within each row. Each region must have at least one cell left empty, but may have more. Empty cells cannot share an edge. Identically numbered cells may not share at edge. All the numbered cells in the puzzle must form a single orthogonally connected group (though the numbers within one region need not do so).
  
• Nuraf, or Araf Nurikabe: Shade some unnumbered cells so that the unshaded cells form islands which can only touch diagonally, and with no 2x2 region entirely shaded. Each island must contain exactly two numbers, and the area of the island must lie strictly between (not inclusive) those numbers.
• Nurimeizu, or Nurimaze: A grid is provided, divided into heavily outlined regions, and wit circles and triangles in some cells and one S and one G. Shade some entire regions so that there is exactly one path of orthogonally connected cells from S to G. This path must include all circles and no triangles. Additionally, no 2x2 region can be all one color, and all the white cells must be orthogonally connected into a single group.. Cells containing any symbol cannot be shaded.
• Oasis, or Oases: A grid is provided with circled numbers in some cells. Shade some empty cells, no two adjacent, and leaving all the unshaded cells connected orthogonally into a single group, but no 2x2 region entire unshaded. Each number tells the number of other numbers you can reach from that number on paths through empty cells.
• Parade Sums: A grid is given that is divided into regions that form paths, with an arrow indicating the start of each path. Fill numbers into some cells of each path so they are consecutive starting from 1, but skipping over empty cells. It is possible for all cells of a region to be empty. Numbers outside the grid give the sums for all numbers in a row or column.
  
• Pentomino Areas: A grid is given which is divided into regions. Place the given pentominoes in the grid so they don't touch, even diagonally, so that the pentominoes do not cross region boundaries and exactly one is in each region.
  
• Pentominoes: This vaguely-named puzzle asks you to place a set of pentominoes into a grid, not touching even diagonally. There may be marked cells where pentominoes cannot be placed. In one version of this puzzle, one set of clue numbers tells how many cells in each row and column are occupied by pentominoes; another tells how many pentominoes include cells in each row or column. Sometimes you only get the clues for the number of cells occupied.
• Pentominous: Divide a grid into pentominoes so that no two pentominoes of the same shape touch along an edge, even if they are rotated or reflected. Some cells contain letters; these must be part of the pentomino of that shape.
• Pentominous Borders: In this variation of Pentominous, some of the borders are given. Each given border must separate two different pentominoes.
  
• Pento-slitherlink: Like regular Slitherlink, but instead of making a single loop, make multiple loops matching the set of pentomino shapes given. These loops cannot touch even at a corner.
  
• Pentopia, or Pentomino Myopia: Shade some empty cells in the grid in the shape of some of the given pentominoes. Those pentominoes cannot touch, not even diagonally. Pentomino shapes cannot repeat, even if rotated or reflected. The arrows in some grid cells show the orthogonal direction(s) where the closest shaded cells are; if there is a tie, all such directions are shown.
• Regional Yajilin: A grid is divided into regions, some of which contain a small clue number in the upper left cell. Shade some non-adjacent cells so that the remaining cells can form a single loop, as in Yajilin, but the clues indicate how many cells in the region are shaded (possibly the one with the clue number),
• Ripple Effect, or Hakyuu: A grid is divided into polyominoes, with a number in some cells. You must place numbers into all the empty cells so each polyomino of size N has all numbers 1 to N, and so that wherever the same number N appears twice in a row or column, at least N other cells separate them.
• Rotator Mosaic: Divide the grid into rotationally symmetric regions, as in Spiral Galaxies, but the dots do not have to be at the center of symmetry. If they are not, there must be a corresponding dot of the same color at the counterpart position.
  
• Round Trip (a different one from the one also called Grand Tour): Draw a loop of orthogonal connections in the grid which may cross itself (both portions going straight through the intersection) but not otherwise overlapping. Numbers outside the grid represent the number of cells crossed by the first straight segment of the loop from that side running along the row or column.
  
• Sashigane: A grid contains some circled numbers, some empty circles, and some triangles. You must divide the grid into L-shaped regions consisting of an elbow in one cell and two straight arms extending from it at right angles. Each circle must be the elbow of a region. If there is a number in the circle, it indicates the total number of cells in the region. Each triangle must be at the end of an arm and pointing at the elbow.
• Slitherlink Out-Liars: A version of Slitherlink in which the numbers inside the loop are correct and the numbers outside the loop are wrong.
  
• Snake Pit: Divide the grid along grid lines into snaky regions, which contain no 2x2 regions nor touch themselves anywhere, even diagonally. Cells with circles must be at the end of a snake, and cells with Xs cannot be at the end of a snake. Numbers in the grid must be in snakes of that size. Two snakes of the same size cannot touch each other orthogonally.
  
• Spokes: Numbers are given in a lattice, each in a spoke-hub shape with sockets for spokes to connect in 8 directions. You must draw orthogonal and diagonal lines between the spokes so that each number is connected to that number of its 8 neighbors, all hubs are connected into one network, and diagonal spokes do not cross.
• Sukazu: Fill a digit into each cell. Within each row, column, and heavily outlined region, the number of instances of each number which appears equals that number.
  
• Sukoro: A grid is provided with numbers in some cells. Place numbers in some of the empty cells so that all the numbered cells form a single orthogonally connected group, two cells with the same number are not orthogonally adjacent, and each number tells the number of its 4 orthogonal neighbors which have numbers.
  
• Tapa-Like Loop: Draw a single loop with orthogonal connections between cells, not going through the cells with clues. Around each cell with numbers, the numbers give the lengths of groups of adjacent cells connected by the loop. If there is more than one number, each represents a separate segment of the loop, though the groups of cells they go through may be adjacent.
• Tapa View, or Canal View: Shade some of the empty cells, forming a single orthogonally connected group, and without shading all of any 2x2 region. Each numbered cell tells the total number of shaded cells it can see in the orthogonal directions up to the next unshaded cell in each direction.
• Tatamibari: A grid has +, -, and | symbols in some cells. You must divide the grid into rectangles along lattice lines so that each rectangle contains one symbol. + symbols must be in squares, and - and | symbols must be in rectangles that are long in the direction of the line.
• Tren, or Parking Lot: Enclose each number in the grid in a 1x2 or 1x3 rectangle. Each rectangle represents a car which can only move in the long direction, and the number tells how many empty spaces (on one or both ends combined) are available in which it can move.
• Yajisan-Kazusan: Some cells in a grid contain a clue consisting of a number and an arrow. Shade some cells, possibly including some of the ones with clues. The shading must follow Japanese crossword rules: Two shaded squares cannot be orthogonally adjacent and the unshaded cells must form a single orthogonally connected group. The clues in unshaded cells must correctly indicate the number of black cells in the direction of the arrow. Clues in shaded cells can be ignored.

• Battleship Sudoku: Locate the fleet in the grid, following standard Battleships rules using shaded ship sections in the grid and numbers outside the grid. Each segment of the ships in the provided fleet has a number on it. Enter these on the ships in the grid; they may be rotated any way. The numbers in thegrid follow standard Sudoku rules.
  
• Even-Odd Sudoku: In some cells without givens, a circle indicates an odd number while a square indicates an even one.
• Isodoku: The grid is drawn as an isometric drawing of a stack of cubes. In place of the usual rows and columns are lines starting at any outside edge and proceeding through opposite edges of the rhombic cells. This generally forces the regions to be irregular.
  
• Little Killer Sudoku: Numbers outside the grid with diagonal arrows indicate the sums of numbers along that line. These sums can include repeated digits.
  
• Minesweeper Sudoku, or Sudoku Mine: The numbers are minesweeper-style clues, not Sudoku fill. Place three mines in unoccupied cells each row, column, and 3x3 region to match the given clues.
• Outside Sudoku: Up to three numbers are given at each end of each row and column. Those numbers must appear within the first three numbers from that side.
  
• Outside Sum Sudoku, or Frame Sudoku: Numbers outside the grid give the sum of the first three entries from that side in the row or column.
• Renban Sudoku: Groups of cells connected by lines act as Renban regions; they must contain a set of consecutive digits, which may be in any order.
  
• Rossini Sudoku: An arrow pointing into the grid along a row or column indicates that the first three numbers in that direction are ascending, and one pointing outward indicates the first three numbers are descending. All possible arrows are given.
• Sandwich Sudoku: Numbers outside the grid give the sum of all numbers between (not inclusive of) 1 and 9 in that row or column.
  
• Skyscraper Sudoku: Numbers outside the grid give Skyscrapers-style clues indicating how many of the numbers in that row or column can be seen from that end, treating the numbers in the grid as the heights of buildings.
• Sudo-Kurve: The regions may be split apart from one another. Bent lines outside the grid connect rows and columns that should be considered part of the same uniqueness group.
  
• Sudoku XV: All boundaries between cells containing two numbers that sum to 10 are marked with an X, and those summing to 5 are marked with a V.
  
• Sujiken: A triangular grid containing half a 9x9 Sudoku grid. In addition to the usual restrictions, no number can be repeated on a diagonal of any length.
  
• Sukaku, or Pencilmark Sudoku: Each cell contains small digits showing all possibilities allowed in the cell.
• Star Sudoku: The grid consists of 6 triangular regions each containing 9 triangular cells, with a 6-cell hexagonal hole in the middle. Regions containing each digit once for this puzzle include the large triangles, 9-cell strips crossing the hole, and 9-cell regions on the edge which include 8 cells in a straight line and one cell which is in an adjacent line by itself.
  
• Strimko, or Chain Sudoku: Essentially a variant on Sudoku with irregular regions; in Strimko, the cells are replaced with circles and lines connect the circles that belong to the same region, which may include diagonal connections.
• Thermo Sudoku: Thermometers given in the grid must contain a strictly increasing sequence of numbers, starting at the bulb (the end with the large circle).
  
• Tight Fit Sudoku: Some cells have a slash. Enter two numbers in these cells so that the smaller number is above the larger. Both numbers coutn as being in the row, column, and region, so the range is larger than the grid size by the number of slashed cells in each of these.
• Tile Sudoku: Some cells are in multiple rows and/or columns, but still take a single digit. Many grid patterns are possible,
• Tridoku: A triangular grid made of 9 triangles each containing 9 triangular cells. Regions not containing repeated digits in this puzzle include the large triangles, the 9 cells along each edge, the 9 cells in the middle rows which have exactly 9 cells (which are shaded for convenience), and 6-cell strips spanning each pair of large triangles in each of three directions.
  
• Tripod Sudoku: Sudoku with irregular regions where the regions are not given, but all points where three region lines meet are indicated with dots. There are no points where four region lines meet.
• Twin Corresponding Sudoku: Two Sudoku grids with givens are provided. The solutions to the two sudokus are functionally equivalent, like a cryptogram (if a 1 appears in a cell in one grid and a 2 in the corresponding cell of the second grid, all 1s in the first grid will correspond with 2s in the second grid).
  
• Vudoku: Shaded Vs connect groups of three adjacent cells in the grid. One number of each V is the sum of the other two.
  

And these are all the other Nikoli-style types I know of which haven't been used in Hunt. Some of these are variants I have seen done only once:

• ABC-Box: Place an A, B, or C in each cell of the grid. The clues for each row and column describe the groups of consecutive cells with the same letter in that row or column. A number tells the length of the group, while a letter tells what letter makes up the group. A question mark indicates a group exists but tells nothing more about it.
  
• Afternoon Skyscrapers: This is a Latin square puzzle where the numbers represent the heights of skyscrapers in each cell, as in regular Skyscrapers puzzles, but instead of the usual clues, shadows are given at the bottom and left edges of some cells, indicating that the skyscraper there is not illuminated from that side due to a taller building. Not all possible shadows are given.
• All or One: A grid is provided, divided into regions each containing three cells, and some cells have numbers given. Fill in 1, 2, or 3 in each empty cell so each region either contains all different or all the same number, and wherever two cells are divided by a region boundary, they have different numbers.
  
• Anraikumozaiku, or Unlike Mosaic: A grid is provided with some shaded cells and circles in some other cells. Divide the unshaded cells into rectangular regions so that each region contains one circle. Regions of the same size cannot share an edge.
  
• Airando, or Island, or Mobiriti, or Mobility: Shade some unnumbered cells. The white cells, including the ones with clue numbers, must remain a single orthogonally connected group (island). Each number tells the number of empty cells that can be reached by orthogonal moves, starting from the number, where other numbers and shaded cells block access. In the version called Mobiriti or Mobility, the numbers are circled.
• Arboretum: A grid is provided with some internal borders drawn (and borders all around the outside) and some circles, some of them containing numbers. Draw additional lines to divide the grid into valid trees. Each tree must have exactly one circled cell, and there must be exactly one path of orthogonal connections without crossing the marked borders from every other cell to the circled cell. A leaf is a non-circled cell with only one undrawn border. A tree must have at least one leaf. All of a tree's leaves are in different rows and different columns. If a circled cell is numbered, its tree contains exactly that many leaves.
  
• Area Division: A grid is provided in which every cell has a letter or is shaded. Divide the lettered cells into regions so that each region has exactly one of each letter used in the puzzle.
• Arithmetical City: Squares are given in rows and columns with some groups of squares in a row or column enclosed in ovals. You are to place a digit from the given range into each square so no digit repeats in a row or column. Read the digits in ovals as multi-digit numbers left-to-right or top-to-bottom. Multi-digit numbers are not allowed to start with 0. Some cells and/or ovals are connected by arrows. A dotted arrow points from a smaller number to a larger one; they may not be the same. A solid arrow points from a number to a positive multiple of that number; they may be the same, but neither may be 0.
  
• Arithmetic Separation: Two long multiplication calculations are given with each digit replaced by a box. Some of the digits may be given. A list of digits is given to fill into these problems, containing all the digits to use. They are all in the right order for each problem, but the two lists of digits are interleaved. There may be multiple ways to fill each calculation but only one way to fill both to make correct calculations.
  
• Arofuro, or Arrow Flow: Place an arrow pointing in one of the four orthogonal directions in each empty cell. The same arrow cannot be placed in two orthogonally adjacent cells. By repeatedly following the arrows one cell at a time, starting at any arrow, you must eventually reach one of the given numbers. The number tells how many starting locations lead to it.
  
• Arrow Maze (a different puzzle from Yajilin), or Arrow Path: A grid is given with numbers in some cells and an arrow (orthogonal or diagonal) in every cell except the one whose number equals the area of the grid. Number all the squares so you can move sequentially from 1 to N, each move going in the direction of the arrow in the cell it starts from.
• Arrow Web: A grid is given with outlined orthogonal or diagonal arrows in every cell. Shade some of the arrows so that every arrow in the grid points to exactly one shaded arrow.
• Battle Stars: A variant of Star Battle. There are no outlined regions in this version, but there are black shaded cells that may not contain stars.
  
• Binary Parquet: A grid divided into 2x2 sections is given along with a set of 2x2 tiles to fill it, marked with black and white squares. Fill the grid with the tiles once each, without rotating or reflecting them. Clue numbers outside the grid indicate the longest run of white cells and the longest run of blck cells in each row and column.
• Binary Stars: Place stars in some cells so each row and column contains exactly one star. Dots in the grid are at the midpoints of two stars. Not all midpoints are gven. A dot can be the midpoint of more than one pair of stars.
  
• Blackout Dominoes: Shade some empty cells in the grid; shaded cells cannot touch along an edge, nor can they share an edge with the edge of the diagram. Place a number in each remaining empty cell so that the numbered cells can be divided into unique dominoes matching the given domino set.
  
• Boomerangs: A hex grid is given, with dots in some cells. divide the grid into boomerangs that consist of a center cell and two legs of equal length coming off that center cell at a 120 degree angle. Each boomerang must contain exactly one of the dots.
  
• Box of 2 or 3: A grid of dots is given, some black and some white, and lines connect some of the nearest neighbor dots. You are to draw nonoverlapping boxes around groups of 2 or 3 adjacent dots; the 3-dot boxes may be bent in an L shape. All black dots must be in a box; the white dots may or may not be included in a box. All the dots in a box must be connected by lines within the box, directly or through another dot. Where lines directly connect dots in different boxes, those boxes must be of different sizes.
  
• Bricks: Fill in numbers from 1 to N, where N is the size of the grid, so each row and column contains each number once. Each 2-cell brick contains an odd number and an even number.
  
• Buraitoraito, or Bright Light: Fill in stars in some empty cells. The number in each black cell tells how many stars can be seen in orthogonal directions from the black cell. Other black cells block the view, but other stars do not.
• Character Battle: A variant of Star Battle. Place the given characters into cells so each row, column, and heavily outlined region contains exactly one of each character. Cells with the same character cannot touch, even diagonally. Cells with different characters may touch only diagonally.
  
• Countries: Divide the grid into regions. Each region must contain exactly one of the lettered cells. The numbers outside the region tell how many of the cells in that row and column are part of the same region as the neighboring cell on the edge of the grid, including that cell. (The cells a clue counts may not all be contiguous.)
  
• Chiyotsui: Shade some cells to form orthogonally connected areas. Each area lies in two regions and is mirror-symmetric with respect to the boundary between those regions. Areas may touch other areas only at a corner. It is possible parts of multiple areas lie in the same region. The numbers tell how many cells in their region are shaded; numbered cells may be shaded.
  
• Chocona, or Chocolate: A grid is given divided into heavily outlined regions and with a number in some regions. Shade some rectangular groups of cells (which may cross region boundaries) so that the given number of cells in each region are shaded. The rectangles can touch only diagonally.
• Column Dance: A grid is given with symbols in many of the cells. Remove (shade) some columns so that the remaining columns have exactly one symbol in each row.
  
• Consecutive Kakuro: Like regular Kakuro, but a white bar is drawn over the borders between adjacent cells which contain consecutive numbers. All possible bars are given.
• CrossRanges: A grid is given with some cells shaded, divided by an X, and containing small clue numbers on some sides of the X.Fill a number in the indicated range into each empty cell so that no number is repeated in a row or column. The numbers in the Xs are clues to the group of consecutive numbered cells ("word") that they face. A clue to a single-cell word is the number that goes in the cell. A clue to a word with multiple cells is thegreatest difference between any two digits in the word.
• Curve Data: A grid is provided, in which some cells contain clues as collections of orthogonal line segments. Connect all the cells in the grid, using orthogonal lines between the centers of cells, to connect each cell without a clue to exactly one cell with a clue, such that the shape of the lines you draw matches the shape of the clue. The lines must have the same orientation as the clue, but the lengths of line segments can vary, as long as they are not zero.
  
• Crystal Mine: Draw a nonintersecting path of orthogonal connections from the entrance arrow to the exit arrow, traveling through every cell marked with a crystal, but never traveling through all four cells of any 2x2 area.
• Dark Knightlines: A variation on No Four in a Row and Tic-Tac-Logic. This time there are four symbols. No two squares separated by a chess knight's move can have the same symbol, and no three in a row in any of the standard eight directions can all have the same symbol.
  
• Deddoanguru, or Dead Angle: Divide the grid into orthogonally connected regions each containing one black circle. Each black circle represents an eye which can see in orthogonal directions up to the next region boundary in each direction. The number on each eye tells how many cells of its region the eye cannot see.
• Detour: Draw a path of orthogonal connections which visits every cell once. The number in a region tells how many times the path turns within that region.
  
• Different Neighbours (not to be confused with Neighbours): Place a number from 1 to 4 in each empty region so that no two regions with the same number touch, even diagonally.
  
• Dominion: Shade some dominoes in unlabeled cells; each shaded cell is orthogonally adjacent to exactly one other shaded cell. Each orthogonally connected group of unshaded cells is an island. Cells with the same label belong to the same island and every island must have a label.
• Domino Construction: An arrangement of dominoes is given, some of them labeled with numbers in one or both halves. Label the remaining ones so that the entire given set of dominoes is used and wherever two cells from different dominoes are adjacent, they contain the same number.
  
• Doppelblock, or Double Block: Shade two cells in each row and column. Place numbers 1 to N-2 (where N is the grid size) in each unshaded cell so that no number is repeated in a row or column. The numbers outside the grid give the sum of the numbers between the blocks in that row or column. In Irregular Doppelblock, some cells may span more than one row or column; if you shade them they count as shaded for all the rows and columns they are in, and if not shaded, they count as a single cell in each row and column.
• Dosun-Fuwari: A grid is provided, divided into heavily outlined regions, and perhaps with black squares which belong to no region. Place exactly one white circle and one black circle in different cells of each region. White circles represent balloons. They can only be placed at the top of the grid, directly under a black cell, or directly under another balloon. Black cells are iron balls. They can only be placed in the bottom row of the grid, directly above a black cell, or directly above another iron ball.
• Dotchi-Loop: Draw a single loop of orthogonal connections which passes through all the white circles and none of the black circles. In each heavily outlined region, the path easier goes turns at every white circle or goes straight through every white circle.
• Dotted Snake: A Snake puzzle, but every third cell along the snake is to be labeled with a dot, The clues outside the grid tell the number of dots in the row or column, rather than the number of snake segments. Some cells are Xed out and cannot be used by the snake.
  
• Double Back: Draw a loop of orthogonal segments through every empty cell. It cannot pass through black cells. Each region must be visited exactly twice.
  
• Douieru: Divide the grid into L-shaped regions. Every circle in the grid is at the corner of an L, and every L has one of the given circles. The black circles mean the legs of the L are of different lengths. Double circles mean the legs are the same length. White circles give no information about the lengths.
• Dutch Loop: Draw a loop that passes orthogonally through every cell in the grid, without intersecting itself. The loop must go straight through cells with white circles and turn in cells with black circles.
  
• Easy as LITS: A grid is provided that is split into regions. Shade one tetromino in each region, following all standard LITS rules, but in addition, clues outside the grid indicate which tetromino is the first one encountered when looking in from that edge of the grid along that row or column.
• Ebony & Ivory: Place a black square or a white circle in every cell. Numbers outside the grid give the longest run of consecutive squares or the longest run of consecutive circles (as indictaed for clues of each type) in the row or column.
  
• Eels: Shade in some cells, dividing the grid into black and white groups called eels. Each eel is a snake-like path of orthogonally connected cells of the same color that doesn't touch itself anywhere, even diagonally. Some cells contain numbers; they must be left white, and indicate the area of the eel they belong to. Numbered cells may also have black and/or white arrows on some of their edges; these indicate whether the adjacent cell in that direction must be black or white.
  
• Endorain, or End Line: A grid is given, divided into regions, with numbers in some cells. Draw separate horizontal and vertical lines, with the ends of each line in different regions. Each number tells how many lines end in its region. Every cell must be on exactly one of the lines.
• Endpoints: A list of symbols are provided (including possibly a blank one) indicating ways to connect the midpoints of edges with lines. Draw a symbol in each cell, without rotation, so that the symbols in each row are all different. Lines from the symbols may connect at the edges of the cells. Dots in the grid are the endpoints of these lines, where a line does not continue in this way. Each dot touches exactly one line and all unconnected ends of lines are marked by dots.
  
• EntryExit: Draw a loop using all the cells in the grid. It can only enter and exit each marked region once.
  
• Eulero: A double Latin square puzzle. Fill in each cell with a number and a letter so that each row and each column contains each number once and each letter once, and each combination of letter and number appears once over the entire puzzle.
• Fillomino Checkerboard: Like regular Fillomino, but with the extra rule that it must be possible to color each polyomino region either black or white so that same-colored regions do not share an edge.
• Fillomino Rectangles: Fillomino crossed with Shikaku. Divide the grid into rectangles along the grid lines. Rectangles may contain zero, one, or more than one number, but their area must match each number they contain. Rectangles of the same area may not share an edge.
  
• Firumatto: A grid has numbers in some cells. Divide it into rectangular regions one cell wide or tall, and one to four cells in the other dimension. Regions may be empty, but each number must be in a region of that size. Two regions of the same size must not share an edge. Four regions cannot meet at a point.
  
• Fobidoshi, or Forbidden Four: The grid contains some circles and some black cells. Place circles in some empty cells so all circles form a single orthogonally connected group, but nowhere are there four circles in consecutive squares of the same row or column.
• Football Pass: A grid is given, decorated with some lines like a soccer field. These lines are purely decorative, except for the two square goalposts on each end. A number of players are given in the grid as white or black circles. Draw two paths, one starting at each circle numbered 1, and traveling in the eight standard directions. Each path must visit all circles of the same color as its starting circle once each, and may not visit circles of the other color (though it may pass through the corners of their cells). Paths can only turn at the circles of their color. Each path must exit the grid between the square goalposts at the opposite side of the field from which it started; paths may not hit the goalposts.
  
• Foseruzu, or Four Cells: Divide the grid into regions of exactly four cells. The number in each cell tells how many of its edges are region boundaries (including the edge of the whole puzzle). Variations with other sizes are possible.
• From 1 to X: Fill in a digit in each empty cell so that each region contains the numbers 1 to X, where X is the area of the region. Two cells with the same number cannot be orthogonally adjacent. The numbers outside the grid give the sum of the numbers in their row or column.
• Full Tapa: Shade in cells as in Tapa. Some cells contain letters and may not be shaded. Add letters to the unshaded empty cells so they spell words as in a criss-cross puzzle, using exactly the given set of words. The words do not all need to be connected. If a one-letter word is given, it cannot touch any other letter.
  
• Furisuri, or Free Three: A grid with circles in some cells is provided. Enclose each circle in a separate block of three cells, which may be straight or bent. Some space is left unused. Each block must be able to slide by one unit using the free space.
• Futari: This is essentially double Hitori. A grid is given with numbers in the cells. Shade some cells, but shaded cells must not share an edge, and the unshaded cells must be connected orthogonally. The unshaded cells in a row or column must not contain any number more than twice.
  
• Fuzuli: Place letters into some of the empty cells so each of the given letters appears once per row and column. No 2x2 area can be completely filled with letters.
  
• Gaps: Shade some cells so exactly two cells in each row and column are shaded. The numbers outside the grid tell how many cells lie between the two shaded cells in that row or column.
  
• Gaidoaro, or Guide Arrow: Shade some empty cells, no two of them adjacent, and leaving the unshaded cells as a single orthogonally connected group. There should only be one path (without backtracking) from each arrow to the single star and the direction of each arrow tells where that path starts.
  
• Gappy: Two cells in each row and each column must be shaded. Shaded cells do not touch, even diagonally. The clues indicate the number of cells between the two shaded cells in that row or column. Equivalent to a special case of Hamusando in which there is enough ham to fill all the non-bread cells.
• Geradeweg: Draw a single loop of orthogonal connections between cells which passes through all the circles. If the path goes straight through a numbered circle, the number indicates the length of that straight segment. If the path turns at a numbered circle, the straight segments on each side of the turn must be the same length, and this length matches the number.
  
• Golem Grad: Shade some snakes in the grid (paths connecting two and including of the given circles). Snakes cannot cross, and no 2x2 region can be entirely shaded. Orthogonally connected unshaded regions are islands. Islands may contain at most one number, and if there is one it tells the area of the island.
• Grades: Place digits 1 to 9 in some cells of the grid, no two of them touching, even diagonally. The numbers at the top and left tell how many numbers are in each row and column. The ones at the bottom and right give the sums of those numbers.
• Grafffiti: This is a Paint by Numbers/Loop puzzle. All the unshaded cells must form a closed loop. 0 may be given as a clue for a row or column to indicate no cells are to be shaded; rows and columns without clues may have any number of groups of shaded cells of any sizes.
• Greater Wall: Shade a group of orthogonally connected cells in the grid. The circles and symbols outside the grid represent Paint by Numbers style clues for the shaded cells in that row or column, with the less than, greater than, and equal signs telling the relationship of each pair of adjacent numbers in a row or column. Rows and columns without these clues may have any number of groups of shaded cells of any sizes.
  
• Gyokuseki, or Gems and Stones: Black one black circle in each row and column, and white circles so that each number outside the grid tells how many circles can be seen in that row or column up to and including the black circle.
  
• Hakoiri: Place circles, triangles, and squares in some empty cells so all the cells with shapes are in one orthogonally connected group, like shapes are never adjacent, even diagonally, and each region contains one of each shape.
• Hamusando, or Ham Sandwich: Place two squares (bread) and the specified number of circles (ham) into each row and column of the grid. The numbers outside the grid tell how many of the circles are between the squares in that row or column.
• Hanare: A grid is given divided into regions, some of them with a number in them. Place a number in some cell of each empty region, always equal to the area of that region. Wherever two numbers are in the same row or column with no other intervening numbers, the number of blank cells between them must equal the difference between the two numbers.
• Heki: Divide the grid into regions of exactly 6 cells. Each number tells how many of the orthogonally adjacent cells are in the same region with it.
• Hexiom: A hex grid is given, along with a set of numbered dots that may repeat numbers. Some dots may be already placed in the grid, and some cells may be marked with an X to indicate thatyou cannot place a dot there. Place dots in the grid so that each dot indicates the number of adjacent dots.
• Hideout Fences: A grid is given with numbers in every cell. Draw a single closed loop along grid lines so that the numbers outside the grid give the sum of the number directly behind each segment of the loop that crosses the row or column, as seen from that end.
• Honey Islands: A hex grid is given with some shaded cells. Shade additional cells so there are six groups of connected unshaded cells, each containing six cells.
  
• Hydra: A multi-headed Snake puzzle. The snake can branch, but cannot contain all cells in any 2x2 region and it cannot loop. Every cell not in the hydra must be orthogonally connected through other such cells to the edge of the grid. All the cells in the hydra that are connect to only one other cell in the hydra are given. One of these, marked with a 1, is the tail. The others are heads, and the clue numbers in them tell the length of the path from that head to the tail, along cells in the hydra.
  
• Hotaru Beam: A grid is given with circles at lattice points. Each circle has an adjacent dot on one of the lattice lines. You must draw a path along the lattice lines from each dot to an edge of one of the circles without a dot. The paths may turn but not touch or intersect. Some circles have a number; the path you draw from that circle's dot must turn that many times.
• Ichimaga: Connect all circles into a single network by drawing lines along the grid lines. The line between any two circles may turn at most once. Each circle must be connected to the number of other circles indicated by its number. Lines cannot cross other lines.
• Increasing Distances: Some circles are provided in a square lattice, with dots indicating the absence of circles. Place the numbers 1 to N one per circle, once each, so that the Euclidean distance between 1 and 2 is smaller than the distance between 2 and 3, which is smaller than the distance between 3 and 4, and so on. (The distances may be irrational square roots.)
  
• Infection: Fill some cells with a number from 1 to 4. Some numbers are given. All the numbers must be connected orthogonally in a single group, and each number must indicate the number of orthogonally adjacent numbers. Orthogonally adjacent cells cannot contain the same number.
  
• Irasuto, or Illustration: Shade some empty cells so that each number in a white cell tells how many empty white cells can be seen in orthogonal directions from that cell, and each number in a black cell tells how many empty black cells can be seen. Numbered cells and cells of the other color block the view.
• Irupu, or I-Loop: A grid is given with circles in some cells. Place 1x3 blocks horizontally or vertically so that there is one covering each circle, they all form an orthogonally connected group, and each block touches two others orthogonally. (These rules require the blocks to form a loop.)
• Island Nations: A grid is given divided into regions. Shade exactly one polyomino in each region so that polyominoes do not touch along an edge. A number in a region indicates the polyomino in that region must contain exactly that many cells. Regions that touch along an edge must contain polyominoes of different areas.
  
• Japanese Arrows: A grid is given with an arrow in every cell (usually in orthogonal directions and numbers in some cells. Place numbers in the cells without numbers so that each number indicates the number of different numbers in the boxes in the direction of the arrow (not including the number in the box with the arrow).
  
• Jemini: Divide the grid into regions, each containing exactly one given letter. Regions of the same shape and orientation must have the same letter in the same position. All instances of the same letter are in regions of the same shape and orientation.
• Jigsaw Logic: Place the given shapes in the grid so that each letter appears once in each row and column. Shapes may be rotated, butnot reflected; rotating a shape does not rotate its letters. Letters on shapes must match the letters given in the grid.
  
• Kabingurodo, or Curving Road: A grid is provided with some cells having circles. Shade some empty cells, no two orthogonally adjacent, leaving all unshaded cells (including the circles) in one orthogonally connected group, so that each path from a circle to any other circle requires at least two turns.
• Kaero, or Ouchihekaero: Move some of the given letters along paths of orthogonal segments, so that all the letters that end up in the same region are the same letter. paths of moving letters cannot cross other letters or paths.
  
• Kanjo: Draw a set of looping paths which go through all grid cells, including the ones with numbers, and using all the given fragments. Each loop contains all instances of one number, and different numbers are on different loops. Loops can cross themselves or each other by passing through in perpendicular directions. Loops cannot cross in cells with numbers.
  
• Kapama, or Sunglasses: Shade some empty cells of the grid to form pairs of mirror image shapes. These shapes cannot touch their mirror images or other shapes except at corners. Each mirror image pair must be connected by one of the given diagonal lines, which must lie perpendicular to the line of symmetry. The numbers outside the grid tell the number of shaded cells in each row or column. In theSunglasses variant, the connecting lines may be in other shapes besides a diagonal line through a single cell, but they must still be bisected by the line of symmetry.
  
• Kapetto, or Set Carpets: Divide the grid into rectangular blocks each containing one number, which is the area of the block. Some cells may belong to no block. (Essentially the same as Shikaku except for some cells being part of no block).
  
• Knossos: Divide the grid into regions along the cell boundaries so that each region contains one given number, which is the total length of the region's boundary.
• Koburin: Shade some empty cells so that each numbered cell is orthogonally adjacent to that many shaded cells, and so that a loop made of orthogonal segments can be drawn through all unshaded, unnumbered cells. Shaded cells cannot be orthogonally adjacent to other shaded cells. Some shaded cells may not be adjacent to numbers.
• Kohi Gyunyu, or Coffee Milk: A grid contains white, gray, and black circles. Connect the circles with horizontal and vertical lines which do not intersect except at circles. Each group of circles connected by lines must contain one gray circle and equal amounts of white and black circles. Lines may not directly connect white and black circles.
  
• Kojun: Fill numbers into the empty cells so each region contains the numbers 1 to N, where N is the size of the region. Orthogonally adjacent numbers must be different. Wherever two numbers are vertically adjacent and in the same region, the upper one must be greater than the lower.
  
• Korekutokonekuto, or Correct Connection: Black and white circles are given at lattice points, some white circles containing numbers. Connect white circles with horizontal and vertical lines, without crossing other lines or black circles, so that all white circles are in a single connected network, the number of connections to each numbered circle matches the number.
• Kuroclone: Shade some cells, forming two orthogonally connected groups in each region which are of the same size and shape (but they may be rotated or reflected). Shaded cells are never orthogonally adjacent to shaded cells in other regions. The arrow-and-number clues indicate that the next cell in the direction of the arrow is part of a group of the indicated size. Cells containing clues are never shaded.
  
• Kuroshiro, or Black and White Loop: A grid is given with black or white circles in many cells. Draw a loop using orthogonal connections through all cells. When two consecutive circles along the loop are the same color, the loop must not turn between them. When the circles are of different colors, the loop must turn exactly once between them.
  
• Kuroshuto: Shade some empty cells, no two of them adjacent, and leaving all the white cells (including ones with clue numbers) orthogonally connected. Each cell with a clue numbers requires exactly one other cell orthogonally that distance away is shaded.
• Lakes: Shade some unnumbered squares so that each number is in a separate region of orthogonally connected unshaded cells equal in size to the number. (This is basically Nurikabe with none of the usual restrictions on the shaded cells; they don't have to be connected and may contain 2x2s.)
  
• Light and Shadow: A grid is given, with some shaded cells and numbers given in both white and shaded cells. Shade additional cells so that each orthogonally connected region of the same color has exactly one number and that number equals the area of the region.
• Line Segment: Draw line segments through groups of 3 or 4 orthogonal or diagonal cells, so that every cell has exactly one segment. Diagonal segments may cross other diagonals at lattice points, but otherwise the segments may not cross. The cells with H, V, or D in the grid must be  crossed respectively by horizontal, vertical, or diagonal segments.
  
• Linesweeper: Draw a single closed loop by connecting orthogonally adjacent empty cells. The numbers in some cells are Minesweeper-style clues, telling how many of the 8 neighboring cells are part of the loop.
• LITSO: Not to be confused with the more familiar LITS puzzle, this puzzle provides a grid (typically irregular and with holes) to be divided into 4-cell regions so that tetrominoes of the same shape (including rotations and reflections) never touch along an edge. Matching shapes are allowed to touch diagonally.
• Loop (Portals): This is a basic loop puzzle (each cell must be used by the loop and the loop is made of orthogonal connections between cells). Some cells contain active portals (with numbers, each number appearing twice) or inactive portals (circle with no number). The loop must go straight through inactive portals. When the loop enters an active portal, it teleports to the like-numbers portal (so these cells will only be connected to one orthogonal cell).
• L-Words: A variation on Sashigane. Divide the grid into L-shaped sections as in Sashigane. Each circled cell must be the bend in an L. Given line segments but lie between two Ls. A list of words is also given. Enter one letter in each cell so that the words can be read along the paths of the Ls. Words may start at either end of an L. Cells with the same letter cannot touch along an edge.
  
• Magic Snail: A grid is given with a heavy outline cutting it into a single spiral, and some numbers in cells. Place numbers in some of the other cells so that each row and column contains each number from 1 to N (N is given) once each, and the letters along the spiral path, starting from the outside, are 1 to N in order repeatedly.
  
• Makaro: A grid is provided which is divided into regions with heavy bars, with numbers in some cells, and some blacked-in squares, some of which have an arrow pointing in one of the orthogonal directions. Fill in numbers in all empty cells so that each region of size N contains the numbers 1 to N once each. Among the (up to) four neighbors of a cell with an arrow, the one pointed to by the arrow must be larger than any other. Identical numbers cannot be orthogonally adjacent.
• Masakuchi: A variant of Makaro in which the cells with arrows also contain a number. The number gives the difference between the largest and second-largest neighboring numbers.
  
• Mathrax: A Latin square puzzle. Circles containing clues appear at some intersections. If the clue is E, all four cells meeting there must be even; if O, all odd; and if a number and an operation, each pair of cells on a diagonal from the clue, when the given operation is applied, produces the given number.
• Maxi Loop: A grid is given divided into regions, each region having a small clue number in one cell. Draw a single closed loop through all the cells in the grid once each. The loop may enter and exit the heavily bordered regions multiple times, but the clue number in reach region tells the number of cells in the longest such path segment in the region.
  
• Maximal Lengths: Draw a loop of orthogonal connections through all the white cells of the grid. The loop does not pass through any black cells that may appear. The clue numbers outside the grid tell the length of the longest segment (measured from cell center to cell center) in that row or column. 0 indicates the loop does not travel along that row or column.
  
• Meadows: Divide the grid along grid lines into square regions, so each region contains one circle. Equivalent to Tatamibari with only + clues.
• Meandering Numbers, Count Number, Worm Farm, or Worms (but see Wamuzu, which is also called Worms): Fill in digits in each cell so that each region contains the numbers 1 to N in order in an orthogonally connected path. Two cells with the same number cannot tough, even diagonally.
• Meandering Words: Same as Meandering Numbers, but insteda of 1 to N, there is a list of words provided to be spelled out by letters placed in the cells.
  
• Mid-Loop: Draw a loop of orthogonal lines between cell centers which passes through all the given dots (which may appear in cell centers or on the lines between cells) and never turns at a dot. Each dot must be at the midpoint of the straight segment of the loop containing it.
• Minesweeper (Pills): Like regular Minesweeper, but the mines occupy pairs of adjacent cells. The mines do not overlap. The clue numbers tell the number of adjacent mines, not the number of cells occupied by mines.
  
• Mintonette: In an irregular grid with circles in some cells, some of them numbered, draw paths of orthogonal segments through every cell. Each path starts and ends in cells with circles, and crosses no other circles or paths. If either circle at an end of a path contains a number, the path must make that many turns.
  
• Mirukuti, or Milk Tea: Connect groups of three circles (two white and one black) with T-shaped lines, so that the two white circles are connected by the straight part of the T and the black one is on the perpendicular segment. Lines cannot intersect except to form the Ts.
• Miti: Draw roads along the cell boundaries, so that all the cells of the grid form a closed loop with no sections wider than a single cell. At each given dot, exactly three roads must meet, and at every other intersection only one or two road segments can be used.
• Modes: Fill each cell with one of the given symbols so that each symbol is used the same number of times in the diagram. The clues outside the diagram give the mode for the cells pointed to by the arrow, that is, they specify the symbol(s) which are most common in those cells, giving all of them if there is a tie.
  
• Mobunanba, or Move Number: Mark a block of three cells (straight or bent) enclosing each given number. Some cells will be unused. The number tells in how many of the four orthogonal directions that block can be moved into unused cells.
• Multiview Skyscrapers: A Skyscrapers variant where each number tells the total number of buildings that can be seen along the row or column plus those along the 45-degree diagonals going into the grid.
  
• Nanbaboru, or Number Ball: A grid is given with numbers in some cells, circles in others, and Xs in still others, along with a given range of numbers. Place numbers in some of the empty cells, and all of the circles, and none of the Xs, so that each number appears once in each row and column.
• Nawabari, or Territory: Divide the grid into rectangular regions so that exactly one given number is in each region. The number tells how many of the four sides of that cell are on the boundary of the region, including the edge of the grid.
• Neibadomino, or Neighbour Domino: Mark dominoes (1x2 regions) in the grid. Some cells may be unused, but all the given numbers indicate how many other dominoes share an edge with that domino. Dominoes with the same number of neighbors cannot share an edge. Dominoes may use 0, 1, or 2 of the given numbers. Dominoes cannot cover all of any 2x2 region. (But there can be empty 2x2 regions and the dominoes do not all have to connect orthogonally.)
• Neighbors: A grid is given with some cells shaded gray and some containing numbers 1, 2, or 3. You are to add numbers to the remaining cells so that each number appears the same number of times in each row and column (i.e. every number three times per row if the rows have 9 cells). Each white cell must touch at least one other number along an edge containing the same number, and each gray cell must not touch any other cells along an edge with the same number. Sky-neighbors is a variant of this with extra cells along each edge of the grid, with the same rules for filling them, but in addition, each number outside the grid acts as a Skyscrapers clue for the row or column of the inner 9x9 that it is next to.
  
• Neighbours: A grid (possibly of irregular shape) is to be divided into regions. Each region must contain exactly one clue number or question mark. If it contains a number, the number indicates how many other regions share one or more units of boundary with the region.
• Nondango: A grid is given divided into regions, with circles in some cells. Shade one circle in each region, so that circles of the same color never appear in a three consecutive cells of any row, column, or diagonal.
• No Four in a Row: A grid is to be filled in with an X or O in every cell (some of them given initially) so that there are not four consecutive identical symbols in a row, column, or 45-degree diagonal.
• No Set in a Row: Place a triangle, circle, or square in each empty cell so that no three consecutive cells in any row, column, or diagonal contain three different symbols or three symbols all the same.
  
• Number Chain: A grid is provided containing numbers from 1 to some maximum N. Draw a path of orthogonal connections from the top left to the bottom right cell which uses each number once (in any order).
• Number Connection: A grid is provided containing the numbers 1 to N once each in some of the cells. Draw an orthogonally connected path through some of the cells that doesn't cross itself and visits all the numbered cells in order.
  
• Nuribou: Shade some empty cells in rectangles one cell wide or tall. which can touch only at corners and only if the sizes of the black strips are different. The orthogonally connected groups of white cells must each contain one number which gives its size, like in Nurikabe.
• Nurimisaki: Shade some empty cells. No 2x2 region can be all the same color. The white cells form a set of interconnected paths. Cells with circles are at the end of a path (only one white orthogonal neighbor) and other white cells must NOT be at the ends of paths. If a circle has a number, it means you can see that many cells from it (including the cell itself, and all in one line since the circled cell has only one white neighbor.)
• Offspring: Place a number from 1 to 9 in each empty cell. (Some numbers are already given.) Cells containing the same number cannot touch, even at a corner. Each cell with a number larger than 1 must touch (along an edge or corner) at least one cell containing every smaller number.
• One to X: Place a number into each cell so that eachoutlined region of X squares contains the numbers 1 to X each once. Cells containing the same number cannot share an edge. Numbers outside the grid tell the sum of the numbers in that row or column.
  
• Orbits: Place a number from 0 to N-1 in each box. Some ellipses appear in the diagram, each completely enclosing one box and running through (behind) others. The number in the box inside the ellipse must equal the sum of the ones the ellipse passes through.
  
• Overlapping Squares: Draw some squares along the grid lines. Squares cannot share edges or corners, but they can intersect as long as both squares go straight through each intersection. Each number in the grid gives the sum of the edge lengths of all squares containing that cell.
  
• Paint by Three(s): Like Paint by Numbers, but the numeric clues are just given as empty boxes. Each gray-shaded box outside the borders of the grid must be filled with a number divisible by 3 and each white box must be filled with a number not divisible by 3.
• Password Path: A grid of letters is given, along with a password. Makea path from the top left to the lower right that can move in the eight principal directions, but does not intersect itself, that only spells the password repeatedly.
• Pata: This is Tapa with the sense of clues reversed. Each number indicates the size of an unshaded group of cells among the up to 8 neighbors.
  
• Patchwork, or Tatami (not to be confused with Tatamibari): A grid is divided into regions of the same size. Each region should be filled with the numbers 1 to N, where N is the size of the region. Adjacent cells must not contain the same digit, and each row and column must contain each digit the same number of times.
• Peintoeria, or Paint Area: A grid is divided into heavily outlined regions and many of the cells have numbers from 0 to 4. Shade all the cells in some of the regions (including cells with numbers) so that out of the 4 cells orthogonally adjacent to each numbered cell, the number indicates how many are shaded, no 2x2 region is all the same color, and all shaded cells are in a single orthogonally connected group.
• Pencils: A grid (with dashed lines) has numbers in some cells and pencil tips in others. Draw pencils in the grid consisting of a 1xN rectangle with a pencil tip against a short end. In addition, draw a line of orthogonal segments of the same length as the pencil ending at each tip. Each number must be in the rectangle of a pencil of that length, each given tip must be attached to a pencil, and each empty cell must be part of exactly one pencil or line.
• Pentomino Division: The same puzzle as Area Division, except with 5 different letters or symbols, and you cannot repeat a pentomino shape.
• Pentomino Relations: Place one of the given pentominoes into each 3x3 box. They can be rotated but not reflected. There are less than, greater than, and equal symbols between the rows and columns of the 3x3 boxes, which indicate the relationships between the number of occupied cells. This puzzle uses a shape made up of the four corners and the center (a quincunx) which is technically not a pentomino but is treated as one for this puzzle.
  
• Pillboxes: Place the given pillboxes into the grid. Pillboxes have a 2x2 shape, they do not overlap, and each is identified by a different number. The numbers outside the grid indicate the sum of the numbers in the pillboxes that occupy any cells in that row or column.
  
• Pills: A grid is given with varying numbers of dots in each cell. Also given are a set of outlines for pills (these look similar to the ships from Battleships but are only outlines and each is accompanied by a number). Place the pills in the grid so that they do not overlap and each contains the number of dots on its label. The numbers outside the grid tell how many dots in the row or column are inside pills.
  
• Pipelink: A grid is given with straight, bent, or crossover pipe segments in some cells. Fill in every empty cell with one of these pipe types so all the pipes form a single loop.
• Place by Product: Shade in the given shapes in the grid, possibly with rotations and reflections, without any of the shapes touching, even at a corner. Numbers outside the grid give the product of all unshaded cell groups in the row or column.
• Pointing at the Crowd: A grid is given with arrows in some cells. Place dots in some empty cells so that each arrow is pointing in a direction that has strictly more dots than any other direction.
• Post-Its: The grid is divided into regions that represent the visible parts of multiple opaque overlapping 2x2 squares. Number them 1 to N in order from the top to the bottom of the stack.
  
• Prime Path: Find a path that goes through each digit once. The path travels only orthogonally, and reading the digits along the path in pairs should result in two-digit prime numbers (a list of two-digit prime numbers is given with this puzzle in competition). No prime is used more than once, and adjacent primes along the path do not have any digits in common.
  
• Prime Place: An irregular grid of squares is given with gray lines running the entire length of some diagonals. Place numbers in the range 1 to N (where N is given for each puzzle) so that the sums of numbers on diagonals with lines is prime, and the sum of numbers on diagonals without lines is not prime. Even one-cell diagonals are included in the line/no-line constraint.
• Products: Place the numbers from 1 to N in the grid, where N is twice the number of rows. Each row and each column must contain exactly two of the numbers. The numbers outside the grid tell the product of the numbers in each row, column, and the main diagonals. (The diagonals may have any amount of each number.)
• Pyramid Climbers: A triangular arrangement of squares is provided with a letter in each square. Each of the squares in the bottom row represents a climber; climbers climb up by moving to one o fthe two squares above their current cell, repeatedly (they do not move sideways). Each cell is reachd by one climber. Each climber's path does not repeat any letters.
  
• Rabbits and Trees, or Raitonanba: Place one white circle (representing a rabbit) and one black circle (representing a tree) in empty cells in every row and every column of a grid, so that each clue number tells how many rabbits can be seen in orthogonal directions from that cell. Rabbits behind trees cannot be seen
• Railway: Same as the Railroad Crossing puzzle (in the index) but the path forms a closed loop.
  
• Raneko: Divide the white cells into regions which each contain one circle. If the circle has a number, it tells the size of its region. The black cells are not part of any region; a black cell with a number tells how many regions share an edge with it.
• Range: Some cells in the grid have an X shape (cross) in them. Fill in a number in each uncrossed cell so that the numbers 1 to N appear in each row and column, where N is the number of uncrossed cells in the row or column. Some crossed cells contain numeric clues on one or more sides of the X. These clues relate to the numbers on that side of the cell in a vertical or horixzontal line until the next crossed cell in that direction or the edge of the grid. If there is only one cell, the cell contains the clue number. Otherwise, the clue gives the difference between the largest and smallest numbers in those cells.
  
• Rassi Silai: Within each marked region, form a path of orthogonal connections through all the cells. The cells that contain endpoints of these paths must not touch, even at a corner.
  
• Rectslider: A grid is given with some black cells, some of them numbered. Slide some of them horizontally or vertically so that the black cells all form rectangles of two or more cells which do not touch orthogonally. The paths of sliding black cells cannot cross. Black cells with numbers must move the distance indicated by the number.
• Recto: Divide the grid into rectangles along the grid lines so one numbered clue is in each cell, as in Shikaku. However, the numbered clues give the sum of the height and width of the rectangle, rather than its area.
  
• Renkatsu: Divide the grid into orthogonally connected regions so that each region contains numbers from 1 to N once each, where N is the size of that region.
  
• Rekuto: Divide the grid into rectangular regions each containing one given number, which equals the sum of the width and height of its region.
• Renban: Fill a number into every empty cell so that the numbers in each heavily outlined region form a set of consecutive numbers, which may appear in any order, and each row and column of the puzzle contains every number from 1 to N once, where N is the size of the grid.
• Rimotoejji, or Remote Edge: Connect all dots with a single loop of orthogonal segments. All the arrows and Xs must be inside the loop. Each arrow points in the direction of the longest straight path of cells inside the loop starting at that cell. Each X has two or more directions tied for the longest such path.
• Ring-Ring: Draw multiple loops that connect the centers of cells orthogonally. Each loop must be square or rectangular in shape. Every cell must be part of at least one loop. Loops may intersect, but only in cells without circles and only if neither loop turns at the intersection. At each black circle the loop must turn, and go straight in the neighboring cells. At each white circle, the loop must go straight, and turn in at least one neighboring cell. (The circles thus work as in Masyu.)
  
• Ripple Arrows: A grid is given with some black cells containing arrows pointing in some of the eight standard directions. Place numbers from the given list in some white cells so each row and column contains each number once, so that each arrow points at a number whose value is also the distance from the arrow to the number.
  
• Roma: A grid is provided, divided into regions with heavy bars, with a circle in one cell and arrows pointing in orthogonal directions in some others. Place an arrow into every empty cell so each region does not contain two arrows pointing in the same direction, and if you follow a path moving in the direction of the arrows starting from anywhere, it ends at the circle.
• Rukkuea: Shade some square regions of cells, possibly including the given numbers. These square regions can touch only diagonally. In any row or column containing parts of two shaded regions of the same size, there must be a shaded region of another size between them. Each number tells how many of five cells (the cell itself and its four orthogonal neighbors) are shaded.
  
• Santoitchi: Shade some of the empty grid cells, no two of them orthogonally adjacent. Divide the remaining cells into regions of size three, which may be straight or bent, and each containing one of the given numbers, which indicates the number of black cells the region shares an edge with..
  
• Sashikabe: Sashigane combined with Nurikabe. All the islands must be L-shaped and one cell wide, as in Sashigane. Circles must be at the bends of islands and arrows at the ends, pointing at the bend. If a number is in a circle, its island must contain exactly that many cells. As in Nurikabe, islands can only touch diagonally, all black (non-island) cells must be connected orthogonally in a single group, and no 2x2 region of all black cells may appear. Islands don't have to contain clues.
• Sashikaku: Divide the grid into rectangular regions with one number in each. The number tells the difference between the width and height of the region.
  
• Satogaeri, or Coming Home: A grid is provided divided into regions with heavy bars, with circles in some cells and numbers in some circles. You must move some circles vertically or horizontally (not both) so that each region contains only one circle. If the circle has a number, it must move exactly that many spaces; circles with 0 cannot move and empty circles may move or stay where they are. The paths of moving circles (including their start and end spaces) may not intersect.
• Scrin, or Screen: Draw rectangular regions in the grid which touch only at corners, and only so that they form a single closed loop. Each circle must be in one of the regions and if the circle has a number, it specifies the area of the region.
  
• Seethrough, Doors, or Open Office: Each cell in the grid represents a room in an office, initially with gaps in every wall between rooms which represent doors. You are to close some doors so that each number indicates the number of other rooms (not including the cell itself) you can see from that room, looking in orthogonal directions through open doors. Compare with Corral.
• Shape Placement: A shape is given made of line segments in cells and/or along boundaries. Some segments are also given in the grid. Draw additional segments so each given segment is part of a copy of the given shape, possibly rotated multiples of 90 degrees and/or reflected. Shapes can touch at a point but not overlap.
  
• Shikaku Liars: In this variant on Shikaku, the clues in the grid are all 1 more or 1 less than the area of the rectangle they must go into.
  
• Shimaguni: In each region, shade a single orthogonally connected group of cells. If the region has a number, that many cells must be shaded. Regions sharing one or more units of edge must have different numbers of black cells. Black cells in different regions cannot be adjacent.
• Shingoki: Draw a closed loop of orthogonal segments which passes through all given circles. The loop must turn at black circles and go straight at white circles. Gray circles have no restriction on turning. If a circle has a number, it tells the sum of the lengths of the straight segments on both sides of the circle, including distance beyond one or more circles if the loop goes straight through them.
  
• Shirokuro: Connect each white circle to a black circle using a horizontal or vertical line. Each circle may have only one line and the lines cannot cross other lines or circles.
• Sign In: + and - signs appear between some pairs of orthogonally adjacent cells. Fill in numbers from 1 to N, where N is the size of the grid, so each row and column contains each number once, and a - indicates the number above or to the left is one less than the number below or to the right, and a + indicates the number below or to the right is one less than the number above or to the left. All possible instances of these clues are given. Compare with Futoshiki and Kropki.
• Skyscrapers Domino Construction: A Domino Construction puzzle, but in addition, numbers given outside the dominoes are clues as in standard Skyscrapers telling how many buildings can be seen from that end of that row or column.
  
• Skyscraper Sums: Like regular Skyscrapers, but the clues give the sum of the heights of buildings that can be seen from that direction.
• Skyscrapers with Diagonals: Clues at the corners outside the grids tell how many buildings can be seen looking along that diagonal. Diagonals may repeat sizes; buildings hide other buildings of equal height.
• Slalom: Draw one of the two possible diagonals in every cell in the grid. There may not be a closed loop of diagonals. Numbers at some vertices tell how many diagonals meet there.
  
• Slash Pack: An irregularly shaped grid contains numbers from 1 to N in some cells. Draw diagonal lines through some cells, never intersecting within a cell, to divide the grid into regions containing each number exactly once.
• Slitherlink (Corners): Draw a loop as in Slitherlink, but the numbers in the cells indicate how many of the four corners of the cell are part of the loop.
  
• Slovak Sums: Place the digits from 1 to N in some cells in the grid so each appears once per row and column. (Some cells will remain empty.) Cells with clues indicate the sum of the orthogonally adjacent numbers and (by the number of dots) how many such numbers are adjacent.
• Sombor: Divide the grid into regions of size 3 or 4, and number the cells in each region from 1 to 3 or 4, in top-to-bottom order, left-to-right within each row. Regions of size 4 cannot share an edge or corner. The given numbers must match the ordering in their regions.
  
• Spans, also called Walls (but distinct from another type also called Walls): Similar to Eminent Domain, but some cells may have walls that don't connect to a clue number, and some walls may connect two clue numbers in the same row or column and count toward both.
• S-Policy: A hex grid is given with some cells shaded. Divide the unshaded cells into tetrahexes so that the given tetrahex shapes each appear once, possibly rotated but NOT reflected.
  
• Square Jam: Divide the grid into squares along the grid lines, so that each cell is in exactly one square (that is, groups of adjacent squares never form larger squares). Four squares may not touch at the same vertex. Each given number in the grid must be inside a square with that edge length.
• Squares and Rectangles: Divide the grid along grid lines into rectangles, each containing exactly one quadrilateral symbol. Regions containing a black square symbol must be square. Regions containing a white rectangle symbol must have different height and width. Any two rectangles that touch along an edge must have different areas.
  
• SquarO: A grid is given with circles at all lattice points (including on the edges) and numbers in the cells. Fill in some circles so each number tells how many of the 4 dots at its corners are filled.
• Star Gaps: A cross between Star Battle and Gaps. Place two stars in each row and column. Stars may not touch, even diagonally, as in Star Battle. But there are no regions in this puzzle; instead, clues outside the grid tell how many blank squares appear between the stars in that row or column.
  
• Starry Night: Place one star, one sun (white circle), and one moon (black circle) in each row and column. The clues outside the grid relate to where the star is in the row or column. If the clue is a sun or moon, it means that symbol is closer to the star. If the star is outside the grid, it is the same distance from the sun and moon.
• Starry Road: A grid is given divided into regions. Place stars in some cells; no two stars may touch, even diagonally. Draw a single closed loop through all the cells without stars. The loop may only pass through each region once.
  
• Stars and Arrows: Place stars in empty cells so each arrow points at exactly one star and each star is pointed at by exactly one arrow, and the numbers outside the grid tell the number of stars in each row and column.
• Stitches: Add some stitches to the grid (nonoverlapping orthogonal lines connecting two adjacent cells in different regions) so each region is connected to each of its neighboring regions exactly once each. Numbers outside the grid tell how many cells in the row or column have stitch-ends in them.
  
• Stostone: Shade some cells, forming an orthogonally connected group within each region and without orthogonal connections to shaded cells in other regions. At least one cell must be shaded in each region; if the region has a number, that many cells must be shaded. Treating each group of shaded cells as a stone, if the stones fall down, they will exactly cover the bottom half of the grid.
  
• Straights, or Str8ts: Fill each empty white cell with a digit from 1 to 9, so that no digit repeats in a row or column. Some cells in the grid are shaded and these break the rows and columns into crossword entries. Each crossword entry must be a "straight," a group of consecutive digits, which may be out of order, such as 5-7-6 or 4-1-3-2. Some black cells may contain numbers, which block that number from the row and column but are not part of any straight. Compare with Sutoreto.
  
• Suguru, or Number Blocks, or Capsules: Place a number in each empty cell so that each heavily outlined region contains all the numbers from 1 to N, where N is the size of the region. Two cells with the same number cannot touch, even diagonally. A version of this puzzle called Capsules where all the regions were of size 5 and some numbers were initially given appeared in a World Puzzle Grand Prix.
  
• Sukima: A grid is provided with some shaded cells and circles in other cells. Mark a region of area 3 (may be straight or bent) covering each circle and not using any shaded cell. Other cells besides the shaded ones will also remain unused. No 2x2 region can be completely covered with marked regions.
• Sukrokuro: Combines some elements of kakuro, sudoku, and kropki. Fill in digits 1 to 9 in empty cells so that numbers given for each crossword entry match the sum of its digits, and so that each row and column contains the digits 1 to 9 once each. Additionally, wherever a white dot appears between two cells, their numbers must be consecutive, and where such dots do not appear, the numbers must not be consecutive.
• Summon: Place a digit in the indicated range into some cells so each outlined region contains each digit once (there is no restriction on rows and columns having these digits). The digits in consecutive cells in each row or column are taken as multi-digit numbers and the clues outside the grid give the sums of these numbers.
  
• Starlight, or Sun and Moon (not to be confused with Moon-or-Sun, nor with another Sun and Moon puzzle type that already appears in the index, related to paths turning or not), also called Munraito: Some planets are given in some cells of the grid which may be illuminated on some quadrants. Place one star and one cloud into each row and column of the grid. Stars illuminate horizontally and vertically to the first star or cloud in each direction, illuminating the two quadrants facing it. The illumination on the given planets must match that provided by the stars.
  
• Suraromu: Make a loop through some of the white squares in the grid, exactly one square from each gate (indicated with a dashed line), and the circled number, which represents the start of the loop and, for convenience, tells you the total number of gates in the puzzle. Some gates are numbered, by printing a white number on the black cell(s) at one or both ends of the gate. The numbers indicate the position in the sequence of gates traversed which that gate must occupy.
• Sutoreto: The given black squares divide the rows and columns into crossword entries. Fill in a digit in each empty cell so that the numbers in each crossword entry form a set of consecutive digits which may be out of order, such as 5-7-6 or 4-1-3-2. Compare with Straights.
• Tairupeinto, Tile Paint, or Crazy Pavement: A grid is provided, divided into heavily outlined regions. Shade some of those regions entirely so the numbers outside thegrid give the number of shaded cells in each row and column.
• Tapa (LITS rules): Shade in cells using the given clues as in standard Tapa, but additionally, the shaded cells can be divided into tetrominoes (L, I, T, and S; no O since a 2x2 cannot be fully shaded) such that two tetrominoes of the same shape never touch along an edge.
  
• Tapa (Transparent): Like regular Tapa, but cells with clues can be shaded. Clues indicate the sizes of orthogonally connected groups within the 3x3 region centered at the clue cell, so a clue cell at the center of a plus shape, which would normally be a 1,1,1,1 clue without the center being shaded, is instead a 5 clue. The rules about the shaded cells being connected and not occupying all of a 2x2 region still apply.
• Tapa (Twilight): Like regular Tapa, but cells with clues can be shaded. Clues in unshaded cells work as in normal Tapa. Clues in shaded cells indicate the lengths of groups of adjacent unshaded cells in the ring of 8 neighboring cells.
  
• Tasquare: Shade some of the empty cells so that all shaded cells are part of square regions. All unshaded cells (including the ones with clues) form a single orthogonally connected region. Number clues indicate the total sizes of black regions touching the clue along an edge. Question mark clues indicate that the area of neighboring black regions is not given, but cannot be zero.
  
• Tasukuea: Shade some cells forming square regions. The cells with clues cannot be shaded. Clue numbers indicate the total size of the shaded squares which share an edge with it. Question mark clues must be next to at least one shaded cell. All unshaded cells (including cells with clues) must form a single orthogonally connected group.
  
• Tenner Grid, From 1 to 10, Zehnergitter, or Grid Ten: A grid 10 cells wide is given, with digits in some cells. Fill the unshaded cells with digits so each digit from 0 to 9 appears once in each row, the numbers in each column sum to the number given at the bottom, and the same digit doesn't appear in adjacent cells (even diagonally).
• Tetoron: Divide the grid into regions of exactly four cells, with exactly two symbols in each region and those two symbols must be different. Regions of the same shape (including rotations and reflections of that shape) must contain the same two symbols.
  
• Tetroid: A grid is given with some shaded cells. Divide the unshaded cells into tetrominoes (L, I, T, S, O). Two tetrominoes of the same type cannot share an edge.
• Tetromino Search: Shade some cells in the grid forming tetrominoes. The tetrominoes cannot touch, even at a corner, and cannot used Xed-out cells. The numbers outside the grid tell how many cells in each row and column are part of tetrominoes. There is no restriction on how many times each tetromino shape may be used.
• Tetrominous: Pentominous with tetrominoes. Divide the entire grid into tetrominoes, like shapes not touching along an edge, and with each letter given in the grid in a tetromino of that shape.
• Tetroscope: Place some pentominoes in the grid so that they do not touch each other, even diagonally. Each tetromino can appear at most once in the grid, including its rotations but not reflections; reflected tetrominoes are considered different in this puzzle. Where a number appears in the grid at the intersection of grid lines, that number of cells out of the ones surrounding it must be part of a tetromino.
  
• Terra X, Terra XV, Terra XX: A grid is given divided into regions, with a number in some regions. Place a digit 0 to 9 into each empty region, so that at each place where four regions meet at a point (marked with a dot) the numbers in the four regions sum to 10 for Terra X, 15 for Terra XV, and 20 for Terra XX.
• Tic-Tac-Logic: A grid is given with Os and Xs in some cells. Place Os and Xs in the remaining cells so each row can column has the equal numbers of Xs and Os, rows can columns do not have three of the same shape consecutively (there may be three of the same shape diagonally), and each row must have a different pattern of Xs and Os, and each column must have a different pattern of Xs and Os. (Rows may have the same pattern as columns.)
• Tiger in the Woods: Draw a path in the grid, starting and ending points to be determined, that visits every white cell. It may not pass through black cells. It may move only in orthogonal direction, and if the next cell after a move is white, it must continue in the same direction (so it can only turn when it reaches a black cell or the edge of the grid, as in tilt mazes). The path may cross itself, but only at right angles (so you may not backtrack).
  
• Toichika: Place arrows pointing in orthogonal directions in some empty cells so each region contains one arrow, all arrows are in pairs that point at each other with no other arrow between them. and two regions with paired arrows do not share an edge.
• Top Heavy: Place numbers into some cells so that each row and column contains each number in the indicatede range once. Other cells remain empty. Cells marked with an X remain empty. If two cells with numbers touch vertically, the one on the top must be greater than the one on the bottom.
• Tower Defense: This puzzle has nothign to do with the video game genre of the same name. It's a Latin square puzzle; place one of the numbers from 1 to N in each cell so each row and column contains each number once. uncircled cells attack up to 4 other cells that are the distance given by its number away from it in an orthogonal direction. Circled cells do not attack, but must be attacked by at least the number of cells given by the number in the circle.
  
• Trace Numbers: Draw a set of paths which collectively visit every cell. Each path starts at a cell numbered 1, and proceeds through the other numbers consecutively, ending in one of the cells with the largest number.
• Trid: A triangular arrangement of circles is given, with the circles connected by lines to make trunctaed triangular cells between the circles. Some circles may already have numbers; you are to place numbers from 1 to N (where N is the length of the longest line) in the empty circles. The numbers along each line must all be different. Any numbers in the triangles indicate the sum of the three numbers in adjacent circles.
• Trigons: A grid of triangles is given with a circle on each edge. Fill in numbers in the given range into the circles so that the sum of the three numbers around each triangle containing a number equals the number in the triangle. Additionally, each possible triple of numbers must appear exactly once as the edges of a triangle.
  
• Trilogy: Fill in a square, circle, or triangle in each empty cell so that no group of three consecutive symbols in a row, column, or diagonal is all the same or all different.
• Trinairo: Fill each empty cell with A, B, or C. Each row and column must have the same number of As, Bs, and Cs. Shaded cells are different from all their orthogonal neighbors.
  
• Trinudo: Divide the grid into regions of size 1, 2, or 3. Each given number must be in a region of the indicated size; a region can have no number or more than one. Regions of the same size cannot touch along an edge.
• Triplets, or One or All: A grid is provided divided into regions of area 3, with symbols (circles, squares, or triangles) in some cells. Place these symbols in every empty cell so that each region contains either all the same symbol or all different, and when symbols are adjacent over a region boundary the symbols are different.
• Triplet Sums: A Latin square puzzle. Fill in a number from 1 to N in each cell so each number appears once in each row and column. Numbers outside the grid give the sums of three consecutive digits in the row or column, and these triplets appear in the order of the clues when multiple clues are given for the same row or column. If the same clue appears twice in a row or column, two different groups satisfy the clue.
  
• Turf: Shade some cells to divide the grid into shaded and unshaded, orthogonally connected regions. Each region must contain a number equal to the size of the region. The region may contain cells with other numbers; these numbers must equal the number of white cells adjacent to cell, including diagonals and the cell itself.
• Twopa: Two copies of an identical Tapa puzzle are given. This puzzle has at least two solutions, maybe more. Find two solutions for the puzzle such that the arrangement of shaded cells around each clue cell is different in the two solutions.
  
• Uncounted Skyscrapers: A Skyscrapers variant in which one building in each row and column, and one with each number, is uncounted. Uncounted buildings count as 0 rather than 1 toward the value of any clues from directions that can see the building, but they still hide smaller buildings.
• Underground: Draw orthogonal connections between some of the cells, forming these cells into a single connected network. A cell may not be connected to only one other cell, but it is possible some cells are not connected at all. Each connected cell therefore either has two connections at right angles, two connections in a straight line, three connections, or four connections. Outside the grid, there are stacked, labeled sets of clues indicating the number of each type of connection for some rows and columns. Each cell where any connections are given at the start is shown with all its connections.
  
• Usotatami: Divide the grid into regions one cell wide or tall and of any size in the other direction, so that each region contains exactly one given number, and that number is NOT equal to the size of the region. Four regions cannot meet at a point.
• Usowan: Shade in some empty cells, never two orthogonally adjacent ones, so that the unshaded cells (including ones with clues) form a single orthogonally connected region. The clue numbers say how many of the (up to four) orthogonally adjacent cells are shaded, but in each region there is one clue that is wrong.
• Vama: Shade some cells in the grid so two cells in each row, column, and region are shaded. All shaded cells muts be orthogonally or diagonally connected into a single group.
• Voxas: Divide the grid into 1x2 (short) and 1x3 (long) regions. Some region boundaries are already drawn, and some of these are marked with a dot. A white dot containing an equal symbol must touch two regions with the same width and with the same height. A black dot with an X must touch one vertical and one horizontal region, and one short and one long region. A gray dot indicates neither the rule for white dots nor the rule for black dots applies.
  
• Walls: See also Spans, another puzzle sometimes called Walls and also similar to Eminent Domain, but differently. Draw walls along some cell boundaries, but not dividing the grid into separate regions. Each numbered clue tells how many cells can be seen from that cell looking in the orthogonal directions and without going through any walls, including the cell itself.
  
• Wamuzu, or Worms (but see also Meandering Numbers which is also called by this name): Connect circles in pairs with paths of orthogonal connections which make a right-angled turn at every step. Every cell must be part of one of the paths.
  
• Water Fun: Shade some cells of the grid so that the clues outside the grid tell the number of shaded cells in their row or column. Wherever a cell is shaded, all other cells in the same region at the same or lower height must also be shaded (so each region has a "water level").
  
• Yagit, or Goat and Wolf: A grid is provided with goats and wilves in some cells, represented by two different symbols, and dots at some lattice points. Add some fences along grid lines, from one spot on the edge to another. Fences may turn only at the given dots. Fences may cross each other anywhere other than the dots. Each region set off by these fences must contain wolves or goats, but not both; regions may not be empty.
  
• Yajikabe, or Yajinurikabelin: Yajilin combined with Nurikabe. Clues in the grid with arrows cannot be shaded and tell the number of shaded cells in that direction, to the edge of the grid. All shaded cells for an orthogonally connected group and there cannot be a 2x2 region entirely shaded. There is no restriction on the number of clues in an island in Yajikabe; Yajinurikabelin's instructions say each island contains at most one number.
• Yajilin-Shapes: Shade in some cells and draw a single closed loop through the others, as in standard Yajilin. However, instead of the shaded cells not touching, the shaded cells must form the given shapes, possibly rotated or reflected. Shapes may not touch, even at a corner. Not all shapes may be used, but each is used at most once. Numeric clues work as in Yajilin, telling how many shaded cells the arrow points to; they may be part of the same or different shapes.
  
• Yajisan-Sokoban: Move some of the given gray squares in paths which do not cross other paths or gray squares; they may cross over the numbers. Each number tells how many gray squares end up in the direction of its arrow. However, if a gray square ends on top of a number, it negates that clue and the number may or may not be correct. Numbers which have been crossed over but not stopped on by squares remain valid.
• Yin-Yang Slitherlink: Draw a loop using the clues as in standard Slitherlink. In addition, the cells inside and outside the loop obey the rules for Yin-Yang: each is an orthogonally connected set and no 2x2 area is entirely inside or entirely outside the loop.
  
• Yokibunkatsu: Divide the grid into regions of five cells, each containing exactly one star, such that they could be folded into open boxes, with the star on the bottom and an open top. Some boundary segments may be already given. There may also be empty regions with no star, which are unrestricted.
  
• Yonmasu: A grid contains some shaded cells and some circles. Divide the unshaded cells into regions containing exactly four cells each including one circle.
• Yunikumaka: Divide the unshaded cells into regions of exactly four cells, containing exactly one dot in its interior. Region boundaries may pass through dots and those dots are ignored and not considered part of any region.

Other puzzle types. This list intentionally omits some puzzle types that appear in WPC events that are not especially Nikoli-like. These include:

• Coins, Darts, and some other simple math puzzles: Coins is "place one of the given numbers in each cell of a grid so the numbers in each row and column sum to the clues given outside the grid," typically with coin-like numbers such as 1, 2, 5, 10, 20, 25, 50. Darts is "which N of these numbers sum to X"?
• Counting puzzles: Many variants of "Count the number of X in this diagram" (which technically does appear in the Mystery Hunt index with a single example from 2010) and other puzzles that involve counting the number of ways to do something.
• Find the differences, find the pairs, and similar observational puzzles: Again, technically find the differences is in the index.
• Word Search with holes, Criss Cross with extra words, etc. These are trivial variations on puzzles in the index in ways to make them harder for competition and/or to give an easy answer key.
  
• Complete the sequence and other knowledge-based puzzles that are generally not considered fair for world competition by modern standards. Again, these may appear in Mystery Hunt and some such puzzles have keywords in the index.
• Encrypted versions of standard puzzles. These are covered by Alphametics in the index.
• Hexagonal versions of standard puzzle types, unless they are interesting in their own right.
• Isometric versions of standard puzzle types (cells are rhombi representing squares on faces of a cube, and rows and columns bend around the faces).
  
• Some one-off variants, ones that are unlikely to be reused, or which are very simple variations of the standard types. These can be interesting in their own right, but would be covered by the standard keyword if included in the index.