To keep my introduction brief, let me just say that I've been a fan of Japanese pencil puzzles, particularly the ones created and/or published by Nikoli (English page) since early 2007, and own a variety of these puzzle books (my inventory). However, it's not always easy to find descriptions of the rules in English, especially for less popular or less well-known games. I've created this page to help solve that problem, by adding rules for new-to-me puzzles as I see them and figure out how to solve them. Also, I'll try to provide rules for some special cases in books I own. Links to each summaries of each puzzle's rules are below, followed by some more intro details (if you're interested).

**Quick links to 98 brief puzzle rules (newest ones in bold):**
Akari / Light Up,
Amibo,
Bag,
Barns,
Block Puzzle,
Capsule Place,
Chokona,
Combination Block,
Conveyor Belt,
Country Road,
Creek,
Cross Counter,
Dosun-Fuwari,
EisBahn,
Erue Ichiru,
Fillomino,
Five Cells,
Goishi Hiroi / Go Stones,
Gokigen Naname,
Hanaregumi,
Hashiwokakero / Bridges,
Hebi,
Herugolf,
Heyawake,
Hiroiiya,
Hitori,
**Honke Yajitatami,**
Hotaru Beam,
Hukumenzan,
IceLom,
Inshi no Heya,
Ittouryoudan,
Juosan,
Kaero,
Kaitouranma,
Kakuro / Cross Sums,
Kanaore,
Keisuke,
Kin-Kon-Kan,
Knight Flow,
Kurodoko (was Kuromasu) / Where Is Black Cells,
Kurotto,
L Route,
Line Line Poker,
LITS (was Nuruomino),
Loop de Route,
Machigai Sagashi,
Makaro,
Makkuro / Makuro,
Masyu,
Mochikoro,
Mushikuizan,
Nagareru,
Nagenawa,
Nansuke,
Noridoko,
Norinori,
Number Link,
Nurikabe,
Nurimeizu,
Odoroku Nakare,
Okiwake,
Orikusu / OLIX,
Panelize,
Purakanasu,
Reflect Link,
Ring Ring,
Ripple Effect,
Roichima,
Rukkuea,
Sashigane,
Seek Words,
Select Equation,
Shakashaka,
Shikaku / Divide by Box,
Shimaguni,
Skeleton Puzzle,
Slalom (Suraromu),
Slither Link,
Sphere/Queue Stone,
Stained Glass,
Sudoku,
Sum Line,
Suukoroheya,
Tasukuea,
Tatamibari,
Tatebo-Yokobo,
Tentai Show,
Tile Paint,
Toichikai,
Tooi,
Yagi to Ookami,
Yajilin,
Yajisan-Kazusan,
Yajitatami,
Yosenabe,
Zabuton.

Here's some more detail on the rules posted here. Most of these come from: (1) English instructions from Nikoli when available, e.g., from Nikoli Puzzles in English or the Penpa series of books; (2) other English instructions available, e.g., at at Nikoli on Wikipedia and Wikipedia's List of Nikoli Puzzle Types; (3) automatic/computer translations (e.g., using Babel Fish or Google Translate) of Japanese instructions, preferably Nikoli's, e.g., from Nikoli Puzzles in Japanese or Nikoli books themselves; and (4) my own interpretation of the rules by trial and error, often using sample solved puzzles in books I own to help. Given that 1 and 2 are often limited, most of the rules here come from 3 and 4 combined, typically by using the Google Translate app on my phone with rules in Nikoli books I own to get English rules that I clarify as needed based on past experience with translated rules and through trial-and-error on actual puzzles and their solutions in the books. Puzzles that appear to require knowledge of the Japanese language will be omitted, but ones using Japanese words/characters that can be solved without knowledge of the language will be included. If you can't find what you're looking for here, you might also try Nikoli-Puzzles [janko.at], which has a similarly-sized list but categorizes puzzles by type (e.g., coloring cells or placing symbols).

Feel free to e-mail me if you find these short rules helpful or unclear, or if you can correct any mistakes I may have made. And feel free to link to this page and/or point others to it for basic Nikoli rule descriptions. Thank you very much for any help you can provide. Special thanks to Grant Fikes and David Olmsted for some rules clarifications/corrections (check out Grant's Cleverly-Titled Logic Puzzle Blog for hundreds of Nikoli-style puzzles he created), to hige_penguin on Twitter for providing some translations and explanations, and to Otto Janko for some title corrections. I will try to add more puzzle rules as I can, so check back now and then for updates.

*NOTE: The 2015-11-29 update for Dosun-Fuwari, Herugolf, Juosan, Kurotto,
Makaro, Nagareru, and Nurimeizu were added before I tried doing these
puzzles, but the source instructions were in English and from Nikoli.
Because of that, I expect that my summaries here are correct, but I will
adjust them if needed once I try some of these puzzles.*

Place light bulbs (circles) so that every square in the grid is lit or contains a light bulb. Numbered cells indicate how many light bulbs are next to it, horizontally and vertically. Light bulbs may go in any white/empty cell and illuminate all the cells vertically and horizontally from it to a black cell or the edge of the board, whichever comes first, but no light bulb may illuminate any other light bulb.

Source: Nikoli Penpa Mix 2, 3, 4; see also Light Up on Wikipedia and Nikoli's Akari Rules

Draw lines horizontally or vertically from marked/numbered cells, such that the lengths of the line is equal to the number in the cell, only one line connects to each numbered cell, each line crosses at least one other line of the same length, and lines do not form closed loops. There may be lines that do not connect to marked/numbered cells. Marked cells without a number may have a line of any length.

Source: Puzzle Communication Nikoli 134 and 135 with trial-and-error. Note: 134 uses solid black cells, while 135 uses circles inside white cells.

Note: This title is tentative.

Draw a single loop without crossings or branches along the grid lines. Every numbered cell must be inside the loop. Numbered cells can see the specified total number of cells vertically and/or horizontally (including itself) before reaching a wall of the loop.

Source: Bag on Wikipedia; clarification by Grant Fikes

Draw a single loop without crossings or branches through the centers of the cells in the grid, passing through every cell in the grid. Lines that enter a gray area cannot change direction until the leave the gray area. Lines are only allowed to cross inside the gray areas. Dark lines in the grid are walls and cannot be crossed by the loop.

Source: Babel fish translation of Barns; sample puzzle in, for example, Puzzle Communication Nikoli 117 with trial-and-error

Divide the grid into pieces that contain permutations of the symbols (numbers, letters, or Japanese kana) of the specified words.

Source: Babel Fish translation of Nikoli's Block Puzzle Rules; clarification by Grant Fikes

Draw capsules (2x1 or 1x2 ovals, half white, half black) so that all circles in the grid have at least one capsule half of the same color adjacent to it vertically or horizontally, cells with an X have no capsule adjacent vertically and horizontally, and long sides of capsules that touch each other may not match in color.

Source: Google Translate of rules in Puzzle Communication Nikoli 136 with some trial-and-error

Note: This title is tentative.

Paint cells of the grid black so that black sections form squares and/or rectangles, and numbered blocks contain the given number of black cells (not necessarily consecutively/joined). Blocks without numbers can have any number of painted cells. Squares and/or rectangles should not share sides.

Source: Puzzle Communication Nikoli 122 with trial-and-error; clarification by hige_penguin

Draw blocks along grid lines so that each block contains one dotted line within it, all blocks must fit together to completely fill the grid, blocks are not squares or rectangles, and the same shaped blocks may not share a side.

Source: Puzzle Communication Nikoli 131, Google translated rules

Note: This title is tentative, and since this puzzle seems to involve more guessing and less logic than I like, I haven't really played through it to test my interpretation of the rules.

Draw arrows in the cells of the grid so that circled arrows (balls) are directed to the "IN" cell. All arrows in a block point in the same direction. Cells in a block that are not used are painted black, and black cells cannot touch vertically or horizontally. All blocks must be used in some way, and the path of one circled arrow (ball) may not flow through another circled arrow (ball).

Source: Puzzle Communication Nikoli 123 with trial-and-error; clarification by hige_penguin

Draw a single loop (road) through the grid where the line passes horizontally or vertically through the center of cells without crossing, branching, or going through the same cell twice. Countries (bold outlined areas in the grid) with numbers have the given number of cells used by the road, and countries without a number must have 1 or more cells used by the path. The road may only enter a country once and exit it once. Adjacent unused cells must not be in different countries.

Source: Country Road on Wikipedia; clarification by David Olmsted

Paint cells black such that numbered intersections have the given number of black cells around them and all white, unpainted cells form a single connected area (the creek).

Source: Babel fish translation of Creek; sample puzzle in Nikoli Puzzle Box 8 with trial-and-error

Draw lines along the dotted lines of the board grid to divide it into squares such that numbers in cells indicate the number of corners of that cell where drawn lines cross.

Source: Google Translate of rules in Puzzle Communication Nikoli 136 with some trial-and-error

Note: This title is tentative.

Place balloons (white circles) and iron balls (black circles) into the grid so that each room (bold bordered area of the grid) contains one balloon and one iron ball. Balloons are light and float, and thus must be placed at the top, immediately under black cells, or under other balloons. Iron balls are heavy and sink, and thus must be placed at the bottom, immediately above a black cell, or above other iron balls.

Source: Penpa 2016

Draw a single loop through the grid from IN to OUT that follows the directions of the arrows. Lines that enter a gray area cannot change direction until they leave the gray area. Lines are only allowed to cross inside the gray areas. The loop must go through every gray area at least once.

Source: Babel fish translation of Ice Barn; sample puzzle in Nikoli Puzzle Box 8 with trial-and-error; clarification by Grant Fikes; title correction by Otto Janko

Place L-shaped blocks of 3 cells each in the grid so that they cover the kanji correctly (what looks like one symbol is the corner, what looks like two side-by-side is the end, question marks can be either), and all white cells are connected (the black cells do not divide the board).

Source: Google Translation of rules in Puzzle Communication Nikoli 132 with trial-and-error.

Fill in all empty cells by dividing the grid into blocks (groups of cells connected horizontally and/or vertically with the same number) so that each block has the same area/size as the number in it and blocks of the same size do not touch each other horizontally or vertically.

Source: Nikoli Penpa Mix 2, 3, 4; see also Fillomino on Wikipedia and Nikoli's Fillomino Rules

Divide the grid into blocks of exactly 5 cells (connected horizontally and/or vertically) by drawing along the grid lines . Numbers indicate how many block edges, including the puzzle border, surround the cell, and a block may have up to five numbers in it.

Source: Penpa 2012 and translation by hige_penguin

Starting from any stone on the board, travel in vertical and/or horizontal lines to pick up all of the go stones by numbering the order in which they are removed from the board. You may only change direction when you pick up a stone, but may not go back in the direction from which you came, and if you travel over a spot where a stone was picked up (numbered), you may not change direction at that point (the stone is no longer present). P.S. -- It looks like more than one solution may exist for these puzzles.

Source: Google Translate and Babel Fish translations of Nikoli's Goishi Hiroi Rules

Draw a diagonal line in every cell in the grid such that numbered intersections have the given number of lines extending from that intersection and lines do not form a closed loop.

Source: Gokigen Naname on Wikipedia

Place one number in every room (bold outlined areas in the grid), where the number is equal to the number of cells in the room, so that the number of empty (white) cells between a number and the next closest one both vertically and horizontally equals the difference between the two numbers.

Source: Google Translate of rules in Puzzle Communication Nikoli 134 with some trial-and-error

Connect all of the islands together by drawing bridges vertically or horizontally between them. The number on each island indicates the number of bridges connected to that island, there can be no more than two bridges connecting a pair of islands, and the bridges may not cross each other.

Source: Hashiwokakero on Wikipedia; see also Nikoli's Hashiwokakero Rules

A snake is the numbers 1 (head) to 5 (tail) sequentially connected vertically/horizontally. Place snakes in the grid so that no two snakes touch each other (share a side), and no snake can "see" any part of another snake (i.e., for a given snake, from the 2-to-1 direction, no other snake's parts can be between its 1 (head) and a black cell / puzzle edge). Black cells with numbers and arrows indicate the snake part number in the adjacent white cell in the arrow's direction; a 0 means there is no snake part from that black cell to the next black cell or puzzle edge.

Source: Penpa 2011, Penpa 2012, and translation by hige_penguin

Move all circles (hit all balls) at least once to bring them to a cell marked H (the holes), one circle to every H, by drawing an arrow vertically and/or horizontally through the cells for each hit. Arrows may not cross other arrow lines, circles, or H cells. Numbers in circles indicate the number of cells it travels on the first move; this decreases by 1 after every move, and the direction of movement can only change at the end of a move. The circle must stop when the number is reduced to 0 or it reaches an H cell. Circles may not move outside of the grid, and cannot stop in the gray areas (water hazards).

Source: Penpa 2014

Paint cells black in each room (bold outlined areas in the grid) so that rooms with a number have that many painted cells in them, painted cells are not connected, white cells are not separated by painted cells, and white cells do not span more than two rooms in a straight line.

Source: Nikoli Penpa Mix 2, 3, 4; see also Heyawake on Wikipedia and Nikoli's Heyawake Rules

Draw lines horizontally or vertically through the centers of the cells to connect each number with a G (goal). The numbers show how many circles the line must pass through, and the direction of the arrow in a numbered cell shows the starting direction for the line.

Source: Puzzle Communication Nikoli 119 with trial-and-error.

Paint cells black such that numbers appear no more than once in each row and column. Painted cells must not touch horizontally or vertically, and white (unpainted) cells must create a single connected area not separated by painted cells.

Source: Nikoli Penpa Mix 2, 3, 4; see also Hitori on Wikipedia and Nikoli's Hitori Rules

This is basically the same as Yajitatami, but shaded cells can't be subdivided and they also serve as borders. So draw lines along the grid lines to divide the board into 1 by X (X = 2+) rectangular rooms (the tatami mats) where numbers indicate the size of the room (number of cells) and arrows indicate the number of rooms in the direction of the arrow, up to shaded cells or the outer border of the board (whichever comes first). There is always a line / room border directly in front of an arrow, and four rooms may not share a single corner.

Source: Puzzle Communication Nikoli 137 with trial-and-error.

Note: This title is tentative.

Draw lines in the grid to create a single, connected network joining all circles (on intersections of grid lines). The network may cross or branch only at circles. Dots on circles indicate where a line of the network connects to the circle. Numbers in circles indicate the number of turns the line makes after leaving the dot and connecting to another circle.

Source: Hotaru Beam on Wikipedia

Each different character in the equation represents a different number. Replace the characters with numbers to solve the equation. Zero will not be a leading digit, and numbers that appear in the equation may also be used as a character.

Source: Google Translate translation of Nikoli's Hukumenzan Rules

Draw a single loop through the grid from IN to OUT that passes through all white cells, passing through all numbered cells in numerical order. Lines that enter a gray area cannot change direction until they leave the gray area. Lines are only allowed to cross inside the gray areas. The loop must go through every gray area at least once.

*Note: this appears to be very much like Ice Barn, but following numbers instead of arrows and the path must go through all white cells.*

Source: Puzzle Communication Nikoli 128 with trial and error; title correction by Otto Janko

Fill all the cells in the grid with numbers from 1 to 9, inclusive, such that no number appears twice in any row or column and the product of the digits in each room (bold outlined areas in the grid) equals the given number in each room.

Source: Inshi no Heya on Wikipedia

Draw one straight, unbending line of any length along the grid lines to divide the field into two pieces of equal area.

Source: Puzzle Communication Nikoli 120 with trial-and-error.

The grid is divided into territories by bold lines. Fill in all cells with a vertical or horizontal dash so that the numbers in territories equal the number of either vertical or horizontal dashes in it (in some cases, there may be equal numbers of both). Horizontal dashes can extend more than three cells horizontally but no more than three cells vertically, and vertical dashes can extend more than three cells vertically but no more than three cells horizontally.

Source: Penpa 2015

Move letters on the board so that each room (bold outlined areas in the grid) contains all appearances of one letter -- all of the As are in one room, all of the Bs are in another room, etc. Movement of letters is indicated by lines that pass through the centers of boxes, bending at right angles as needed, with an arrow at the end indicating the destination cell. Lines cannot cross or branch.

Source: Babel fish translation of Kaero; sample puzzle in, for example, Puzzle Communication Nikoli 117 with trial-and-error

Draw straight lines on the puzzle grid, from border to border, to divide the grid into partitions. Each partition must contain at least 1 white circle, or at least 1 black circle, but cannot contain both black and white circles.

*Note: the name of this puzzle means "cutting the Gordian knot".*

Source: translation by hige_penguin

Place a number from 1 to 9, inclusive, in each cell so that the sum of the numbers in each block (vertical column or horizontal row of connected white cells) is equal to the number at the top or left of that block cells and each number is used no more than once in each block.

Source: Nikoli Penpa Mix 2, 3, 4; see also Cross Sums on Wikipedia and Nikoli's Kakuro Rules

Fill the grid with the given (Japanese) words. Each word has a number and direction; the word starts in the matching numbered cell in the grid and begins extending the direction specified. Each letter/character must be placed horizontally or vertically adjacent to the last. Some letters/characters may be used by more than one word.

Source: Sample puzzle in Nikoli Puzzle Box 6, 7, 8 with trial-and-error

Basically a number crossword where you have to supply the black cells. Place numbers from clues in the grid (across = left to right, down = top to bottom) where number edges meet the puzzle edge or a painted black cell. Black cells may not touch horizontally or vertically, and all white cells must create a single connected area not separated by black cells.

Source: translation by hige_penguin

Place diagonal lines in cells (mirrors) such that each room (bold bordered area in the grid) contains exactly one mirror, and letter-number pairs at the edges of the grid can be connected by straight lines that bounce of the same number of mirrors as the number in the letter-number pair. For example, B2 at one edge must connect to the other B2 by straight vertical and horizontal lines (passing through the centers of the cells) that bounce off of 2 mirrors in the grid.

Source: Kin-Kon-Kan on Wikipedia (page has been deleted)

Draw a single, closed loop without branches or crossings through the grid that goes through all white circles, does not go through any black circles, and goes through white triangles as needed (they're optional). The line much alternate between moving to a vertically or horizonally adjacent symbol and making a chess knight's move (2 squares vertically then 1 square horizontally, or 2 squares horizontally then 1 square vertically).

Source: Google Translate of rules in Puzzle Communication Nikoli 128 with some trial-and-error

Paint cells black such that each numbered cell can see the specified total number of cells vertically and/or horizontally (including itself) before reaching black cells or edges of the grid. Black cells may not touch horizontally or vertically, and all white cells must create a single connected area not separated by black cells. Numbered cells may not be black.

Source: Kuromasu on Wikipedia and Nikoli's Kurodoko Rules

Color cells in the grid black so that each circle with a number has that number of consecutive black cells extending from it, vertically and horizontally. There may be multiple lines of black cells extending from a single circle, empty circles may have any number of black cells around them, and cells with circles may not be colored black.

Source: Penpa 2013.

Divide the grid into only L-shaped blocks 1-cell wide. Circles mark the L's knees/corners (places where the Ls bend at a right angle), and arrows indicate an end of an L and point towards the knee/corner. An L-shaped block may have any number of cells in it (minimally 3 to create an L).

Source: Google Translation of rules in Puzzle Communication Nikoli 134 with trial-and-error.

A 5x5 grid of playing cards is the board, and each row and column is labeled with a poker hand (e.g., one pair, full house, straight). The suits for all cards are given. Fill in the missing card numbers so that all rows and columns have the type of poker hand specified. {Note: The rules I saw provided graphic examples of the hand types, making translation from Japanese fairly simple. I'm not sure if this description is clear enough, but it should be easier to understand once you see this puzzle. I can try to clarify if people request that though.}

Source: Puzzle Communication Nikoli 126

Color four consecutive squares (tetrominoes) in each area surrounded by bold lines such that similarly shaped or rotated tetrominoes do not touch except possibly at corners, the colored squares form a single connected area, and the colored squares do not form areas of 2x2 or larger.

Source: Nikoli Penpa Mix 4; see also LITS on Wikipedia

Draw one or more closed loops along the grid lines through circles with the same number. Circled numbers indicate the number of times a line turns/bends before reaching the next circled number of the loop. Loops may not branch, but they may cross each other.

Source: Puzzle Communication Nikoli 131 with trial-and-error

Note: This title is tentative and the Japanese appears to be "ruupu do ruuto", which I think is the equivalent of "loop de route".

A find-the-differences puzzle -- locate parts of the given pictures that are not the same in both.

Source: Nikoli's Machigai Sagashi Rules

The grid is divided into rooms by bold lines. Fill all empty cells with numbers so that each room has numbers 1 through the number of cells it contains, and numbers in one room may not be adjacent to the same number in another room. Black cells with arrows point to the vertically or horizontally adjacent cell with the largest number of those (up to) 4 cells surrounding it.

Source: Penpa 2014

Fill the crossword-like grid with numbers according to the given clues, which are numbered and grouped by answers that read across (left to right horizontally) and answers that read down (top to bottom vertically). Clues are given in terms of the answers to other clues; for example, using a sample game from Nikoli, 1 down minus (ひく) 8 across, 1/2 (2分の1) of 4 down, 7 down times (倍) 8, 2 across plus (たす) 6 down. For puzzle clues using Japanese words, treat the words as variables and all clues as multiplications -- if there's no number in the clue, then it's 1, just the word/variable itself. This wasn't too hard to understand once it was explained to me, but if I didn't explain it well here, let me know.

Source: Sample puzzle in Nikoli Puzzle Box 6, 7, 8 with trial-and-error; explanation of Japanese word clues from hige_penguin

Draw a single loop without crosses or branches with lines extending horizontally or vertically through the centers of the cells. The loop must include all cells with white and black circles. White circles indicate that the path goes straight through the cell and makes a 90-degree turn in the cell before it, the cell after it, or both. Black cells indicate that the path makes a 90-degree turn inside the cell, with the path extending straight for two cells before and after it.

Source: Nikoli Penpa Mix 2, 3, 4; see also Masyu on Wikipedia and Nikoli's Masyu Rules

Paint cells black to create rectangular and/or square rooms of white cells with at most one number per room and size/area equal to the number in each room. Rooms may not touch vertically or horizontally, but must touch at least one other room diagonally so that all rooms are connected. Black cells may not form areas of 2x2 cells or greater.

Source: Mochikoro on Wikipedia (page has been deleted); clarification by Grant Fikes

Each square in the equation represents a single digit, 0-9. Replace the squares with numbers to solve the equation. Zero will not be a leading digit, and numbers that appear in the equation may also be used in the square(s).

Source: Google Translate and Babel Fish translations of Nikoli's Mushikuizan Rules

Draw a line horizontally, vertically, or turning through the centers of cells to create a single, continuous loop in a direction that does not cross itself, branch off, or go through the same cell twice. The line must go through cells with black arrows, and these arrows indicate the direction of the loop. White arrows in black cells indicate a wind blowing in the given direction until it reaches another black cell or the grid border; the loop line may not move into this wind. When a line enters a cell where the wind is blowing from the side, it must turn in the direction of the wind. The line cannot hit the grid border or enter black cells.

Source: Penpa 2016

Draw any number of square and/or rectangular loops in the grid, using vertical and horizontal lines through the centers of the cells, such that blocks with numbers contain line segments in the given number of cells of that block. Loops may cross in any cell, but cannot share line segments and cannot change direction at a crossing. Some loops may be completely separate from others (not crossing any other loops).

Source: Nikoli-Puzzles [janko.at] with clarifications from hige_penguin

Place all of the given numbers into the crossword-like grid. (This is like a crossword with numbers, where you have all the answers and have to figure out where they belong, instead of knowing where the answers belong and having to figure them out.)

Source: Sample puzzle in Nikoli Puzzle Box 6, 7, 8 with trial-and-error

Paint cells black such that each numbered cell can see the specified total number of cells vertically and/or horizontally (including itself) before reaching black cells or edges of the grid. Black cells must form 2x1 or 1x2 areas, and these areas may not touch horizontally or vertically. All white cells must create a single connected area not separated by black cells. Numbered cells may not be black.

*Note: this seems like kuromasu/kurodoko, just with 2x1 and 1x2 black
areas instead of 1x1 black cells, but I may be missing something.*

Source: Sample puzzle in Puzzle Communication Nikoli 117, 118 with trial-and-error

Paint cells black such that each block contains two black cells with black cells forming 2x1 or 1x2 areas that may not touch horizontally or vertically. Note that the black cell pairs may cross the bold block borders.

Source: Penpa 2011

Connect pairs of the same number together with lines that pass horizontally and/or vertically through the centers of cells. Lines cannot cross or branch off, and cannot go through the same cell twice.

Source: Nikoli Penpa Mix 2, 3, 4; see also Number Link on Wikipedia and Nikoli's Number Link Rules

Paint cells black so that the grid is full of white areas, each with a single number and size equal to that number, separated by black cells (walls) that are all connected and do not form 2x2 or larger areas. Numbered cells must not be painted black, and white areas must be separated from each other horizontally and vertically by black walls.

Source: Nikoli Penpa Mix 2, 3, 4; see also Nurikabe on Wikipedia and Nikoli's Nurikabe Rules

The grid is divided into rooms by bold lines. Create a maze that goes from S to G across only white cells by coloring cells black to make walls. All cells in a room must be either black or white. All white cells must remain connected, but cannot form a loop. Neither white not black cells can form 2x2 or larger squares. Rooms with S, G, circle, and triangle cannot be painted black; all of the cells in the room with the circle will be on the shortest path from S to G, but none of the cells in the room with the triangle will be.

Source: Penpa 2015

Place 1x2 or 2x1 all-white and/or all-black tiles in the gird such that cells of the same color do not share a side, all tiles including 1x1 given tiles are connected vertically and/or horizontally, and a 1x2/2x1 tile may not form a straight line with a 1x1 tile. Four tiles are allowed to meet at a single corner.

Source: Puzzle Communication Nikoli 135 with trial-and-error.

Note: This title is tentative.

Put one or more numbers in each room (bold outlined in the grid) such that the numbers sum to the room's size (number of cells), numbers are not repeated in the same row and column, and each number in each room must connect vertically and/or horizontally to at least one number in another adjacent room.

Source: Puzzle Communication Nikoli 135 with trial-and-error.

Note: This title is tentative.

Draw a single closed loop of vertical and horizontal lines through the centers of grid cells such that cells marked: "O" have no lines through them, "L" have lines that bend in them, "I" have lines that go straight through them, and "X" have lines that cross (vertically and horizontally). Lines cannot cross in a cell other than those marked "X".

Source: Puzzle Communication Nikoli 123 with trial-and-error; clarification by hige_penguin

The puzzle name is Paneraizu in romaji, which I'm taking to be Panelize. Draw vertical and horizontal lines along the grid lines to divide the grid into square and rectangular regions. Circled numbers must be contained within a square with side length equal to the number (e.g., a cell with a circled 3 lies inside a 3x3 square region). Intersection points of the grid lines may not have four drawn lines coming out from them (+s are not allowed, but Ts are OK), and squares of the same area may not share a side.

Source: Puzzle Communication Nikoli 127 with trial-and-error; I'm not sure this description is completely correct, but it does seem to work with the puzzles I've tried so far.

Fill the grid with spelled-out numbers so that where a number is given at an intersection, the spelled-out numbers that cross there sum to the given number. Note that the rules provided specify how certain numbers should be written, and (in my experience) Japanese numbers typically use a format of number * power of ten. So for example, 234 would be spelled like 2 100 3 10 4. If I've made some mistake here, hopefully someone with more Japanese knowledge can correct me.

Source: Google Translation of rules in Puzzle Communication Nikoli 132 with trial-and-error.

Draw a single loop without branches by drawing lines horizontally and/or vertically through the centers of cells. If a cell has a plus sign in it, two lines intersect in it; these are the only places lines may intersect. Cells with triangles in them reflect the line at right angles, and all triangles must be touched by the lines. Numbered triangles indicate the total number of cells (including the triangle's cell) that the beam travels horizontally and vertically before changing direction.

Source: Babel fish translation of Reflect; sample puzzle in Nikoli Puzzle Box 7, 8 with trial-and-error

Draw square and/or rectangular hoops (rings) through the centers of grid cells such that lines go through all open/white grid cells. Hoops are allowed to overlap and cross each other, but they may not touch at a single corner.

Source: Puzzle Communication Nikoli 135 with trial-and-error

Note: This title is tentative.

Number all cells in each room (bold outlined areas in the grid) such that each room contains consecutive numbers starting from 1, and if a number appears more than once in a row or column, they are separated by at least that number of cells. For example, a room with 4 cells must contain the numbers 1, 2, 3, and 4, and two 3s in the same row must be separated by 3 or more cells.

Source: Nikoli Penpa Mix 2, 3, 4; see also Ripple Effect (puzzle) on Wikipedia and Nikoli's Ripple Effect Rules

Fill all cells in the grid with arrows that point up, down, left, and right such that all arrows within a black-bordered room point in different directions, and following the path of the arrows from each cell will end at the black circle(s).

Source: Puzzle Communication Nikoli 131 with trial-and-error

Note: This title is tentative.

Shade cells in the grid black to form squares that do not share sides. Numbered cells indicate how many cells of the numbered cell itself, and the four cells immediately adjacent vertically and horizontally are shaded black. Shaded squares of the same size cannot follow each other in the same row or column (they can repeat later if a different size square comes between them).

Source: Google Translate of rules in Puzzle Communication Nikoli 136 with some trial-and-error

Note: This title is tentative.

Divide the grid into only L-shaped blocks 1-cell wide. Circles mark the L's knees/corners (places where the Ls bend at a right angle), and a number in a circle indicates how many cells are in the L containing it. Arrows indicate an end of an L and point towards the knee/corner. An L-shaped block may have 0-3 marks (arrows and circles, numbered or not) in it.

Source: Penpa 2012 and translation by hige_penguin

A typical word search puzzle -- find the words in the grid; words can read up, down, left, right, or diagonally.

Source: Nikoli's Seek Words Rules

Select one item from each column of the grid to create correct mathematical equations. Each item can be used only once, and in a grid of X rows, the selections must be made so that there are X correct equations.

Source: Sample puzzle in Puzzle Communication Nikoli 117 with trial and error

Place black "triangles in squares" in white cells of the grid such that parts of the grid remaining white always form a rectangle or square. Numbers indicate how many black triangles are around the cell, vertically and horizontally.

Source: Penpa 2011, Penpa 2012

Divide the grid into rectangles and/or squares (boxes) such that each box drawn contains one number and that number is the size (area) of the block.

Source: Shikaku on Wikipedia and Nikoli's Shikaku Rules

Shade in a polyomino in each area surrounded by bold lines such that no two polymoinoes touch except possibly at corners, no two touching regions contain polyominoes of the same size, and a numbered region contains a polyomino of that size.

Source: GLmathgrant's explanation of Shimaguni; sample puzzles in Puzzle Box 9

Place the given words into the empty (skeleton) grid so that all of the words link up crossword-style. A word of X characters must go into a horizontal or vertical line of exactly X characters.

Source: Puzzle Communication Nikoli 117 and past experience of similar puzzles

Move balls in the grid horizontally only, not passing through walls (bold vertical grid lines), so that numbers indicate how many cells without balls are between it and the floor (bold horizontal grid line) in the same column. Motion is indicated by arrows that cannot hit or cross any other arrows or balls, and not all balls are required to move.

Source: Google Translate of rules in Puzzle Communication Nikoli 136 with some trial-and-error

Note: This title is tentative.

Draw a single loop without crossings or branches by drawing lines horizontally and/or vertically through the centers of cells, starting and ending at the circled number, which indicates the total number of dashed lines (gates) on the board. The loop must pass perpendicularly once through each gate, numbered gates indicate the order in which the gates are passed, unnumbered gates may be crossed in any order, and each gate may be crossed only once. If a numbered black cell is next to more than one gate, then the number refers only to the gate which has that same number on both ends.

Source: Slalom; sample puzzles in Puzzle Box 9, Puzzle Communication Nikoli 117, 118; Nikoli's Slalom Rules; clarification by Grant Fikes

Draw a single loop without crossings or branches by connecting adjacent dots with horizontal or vertical lines. If a cell has a number in it, then it must have exactly that number of lines surrounding it. If a cell is empty, then it may have any number of lines (from 0 to 3).

Source: Nikoli Penpa Mix 2, 3, 4; see also Slitherlink on Wikipedia and Nikoli's Slitherlink Rules

Paint areas black according to the rules indicated by the color of the circles at their intersection: a black circle means more of the neighboring areas touching it are painted than unpainted; a white circle means more of the neighboring areas touching it are unpainted than painted; a gray circle means there are an equal number of painted and unpainted neighboring areas touching it.

Source: Stained Glass on Wikipedia

Place a number from 1 to 9, inclusive, in each cell such that every row, column, and 3x3 block (outlined in bold) contains all of the numbers from 1 to 9 only once.

Source: Nikoli Penpa Mix 2, 3; see also Sudoku on Wikipedia and Nikoli's Sudoku Rules

Place a one-digit number from 1 to 9 in every white cell, where numbers given as clues are the sums of the rows/columns. X cells between black cells / puzzle edges are treated as X-digit numbers. The same one-digit number may not be repeated in a row or column.

Source: translation by hige_penguin

Place one or more of the numbers 1, 2, 3, and 4 into each black-bordered room of the grid so that each digit touches that number of other digits vertically and/or horizontally, each room has all cells either empty or filled with numbers, and all numbered cells are connected together.

Source: Puzzle Communication Nikoli 131 with trial-and-error

Note: This title is tentative.

Paint cells of the grid black so that black sections form squares and cells with numbers in squares touch squares with total areas equal to the given number. A cell with a square but no number may touch any number and size of black cells greater than zero. All white cells must create a single connected area not separated by black cells. Cells with squares remain white.

Source: Puzzle Communication Nikoli 123 with trial-and-error; clarification by hige_penguin

Divide the grid into rectangles and/or squares (boxes) such that each box contains one symbol (+, -, or |), boxes with a + are square (height and width are equal), boxes with a - are wider than they are tall, boxes with a | are taller than they are wide, and no four boxes share the same corner.

Source: Tatamibari on Wikipedia

Place a vertical or horizontal line through the center of every cell such that shaded numbered cells have the given number of horizontal and/or vertical lines extending out of it and unshaded numbered cells have a line with length equal to the given number passing through it horizontally or vertically.

Source: Tatebo-Yokobo on Wikipedia

Divide the grid into blocks (groups of cells connected horizontally and/or vertically with the same number) so that each block contains a circle, and the block is symmetric under a 180-degree rotation about the circle (the shape looks the same if you rotate it 1/2 turn). Blocks with black circles are then painted black, while blocks with white circles are left unpainted. The result should be a picture.

Source: Nikoli Puzzle Cyclopedia and Nikoli's Tentai Show Rules

Paint cells black in the grid such that each row and column has a total number of painted cells equal to the number at the left and top of the grid. Blocks in the grid (bold outlined areas in the grid) must be either fully painted or fully unpainted. The result should be a picture.

Source: Nikoli Puzzle Cyclopedia

Place one arrow pointing up, down, left, or right in each bold-bordered room of the grid so that each arrow points to one other arrow that points at it and there is at least one room's worth of empty cells along the line of sight between arrow pairs.

Source: Puzzle Communication Nikoli 131 with trial-and-error

Note: This title is tentative.

The kanji 上 (up), 下 (down), 左 (left), 右 (right) indicate that white cells extend in that direction more than the other three directions. Cells with a kanji character will not be painted black. Black cells cannot touch each other vertically or horizontally.

Source: translation by hige_penguin

The puzzle name means Goats and Wolves. Draw vertical and horizontal lines on the grid, going from one grid edge to any other grid edge (i.e., no loops within the grid), optionally making right angle turns only where black dots are located, to divide the grid into regions where each region contains only goats or only wolves (not both, and not empty). Lines may cross each other anywhere in the grid except at the black dots.

Source: Puzzle Communication Nikoli 126 and 127 with trial-and-error; Nikoli's Yagi to Ookami rules translation and interpretation by Fred Schneider

Draw a single loop through the grid where the line passes horizontally or vertically through the center of cells without crossing, branching, or going through the same cell twice. The line cannot pass through numbered cells, which indicate how many black cells are in the direction of the arrow in that cell, or black cells, which cannot touch each other horizontally or vertically. Every cell the loop doesn't pass through must either be a numbered clue cell or a black cell.

Source: Nikoli Penpa Mix 3, 4; see also Yajilin on Wikipedia and Nikoli's Yajilin Rules; clarification by Grant Fikes

Paint cells black such that numbered cells indicate the number of black cells in the direction of the arrow in those cells. Black cells may not touch horizontally or vertically, and all white cells must create a single connected area not separated by black cells. Numbered cells must be painted black if they contain false clues, but numbered cells painted black do not necessarily contain false clues.

Source: Yajisan-Kazusan on Wikipedia

Draw lines along the grid lines to divide the board into 1 by X (X = 2+) rectangular rooms (the tatami mats) where numbers indicate the size of the room (number of cells) and arrows indicate the number of rooms in the direction of the arrow. There is always a line / room border directly in front of an arrow, and four rooms may not share a single corner.

Source: Puzzle Communication Nikoli 135 with trial-and-error.

Note: This title is tentative.

Draw vertical and/or horizontal arrows in the grid to move all numbered balls into gray pots such that the drawn arrows do not cross or branch and the sum of the numbers on the balls equal the number in the gray pots. If a gray pot has no number, there must still be at least one ball placed in it.

Source: Puzzle Communication Nikoli 135 with trial-and-error.

Note: This title is tentative.

Place integers in the cells so that the sum of all integers in each black-bordered room of the grid equals the area of (number of cells in) that room, the same numbers do not touch vertically or horizontally, and all numbers are connected together.

Source: Puzzle Communication Nikoli 131 with trial-and-error

Note: This title is tentative.

Here I briefly describe how these 20 puzzles are connected so that you will (hopefully) be able to solve them all and get to the final answer. The basic procedure, after solving the first puzzle and answering a question about it, is to use the previous puzzle's answer to help solve the current puzzle and answer a question about the current puzzle, which gets used to solve the next puzzle, etc. As with my rules above, please let me know if there are any mistakes here. Thanks, and thanks (again) to Grant Fikes for help and corrections.

- Kakuro -- Answer A is the number in the outlined cell of the solved puzzle.
- Slither Link -- Replace "A" in the puzzle with the number from Answer A. Answer B is the total number of 3s inside the loop of the solved puzzle.
- Nurikabe -- Replace "B" in the puzzle with the number from Answer B. Answer C is the number of black cells in the marked row of the solved puzzle.
- Akari -- Replace "C" in the puzzle with the number from Answer C. Answer D is the number of light bulbs in the marked row of the solved puzzle.
- Yajilin -- Replace "D" in the puzzle with the number from Answer D. Answer E is the total number of black cells in the solved puzzle.
- Ripple Effect -- Replace "E" in the puzzle with the number from Answer E. Answers F and G are the numbers in the outlined cells marked as F and G.
- Number Link -- Replace "F" and "G" in the puzzle with the numbers from Answers F and G. Answer H is the number of bends in the line connecting the two 4s in the solved puzzle.
- Masyu -- If the number for Answer H is odd, then replace "H" in the puzzle with a white dot. If the number for Answer H is even, then replace "H" in the puzzle with a black dot. Answer J is the number of white cells in the marked column of the solved puzzle.
- Fillomino -- Replace "J" in the puzzle with the number from Answer J. Answer K is the number in the outlined cell of the solved puzzle.
- LITS -- Solve the puzzle, then count how many times each shape (L, I, T, and S) appear in the solution. All rotations and reflections of a given shape are added together. Answer L is the letter of the shape that appears Answer K times.
- Hitori -- Letters LITS in the puzzle are solved by blacking out the one letter matching Answer L and leaving the other three white. Answer M is the number of black cells in the marked row of the solved puzzle.
- Heyawake -- Replace both "M"s in the puzzle with the number from Answer M. Answer N is the total number of rows that contain 3 black cells in the solved puzzle.
- Akari -- Replace "N" in the puzzle with the number from Answer N. Answer P is the total number of light bulbs in the solved puzzle.
- Kakuro -- Replace both "P"s in the puzzle with the number from Answer P. Answer R is the number in the outlined cell of the solved puzzle.
- Yajilin -- Replace "R" in the puzzle with the number from Answer R. Answer S is the number of black cells in the marked row of the solved puzzle.
- Nurikabe -- Replace "S" in the puzzle with the number from Answer S. Answer T is the number of black cells in the marked column of the solved puzzle.
- Number Link -- Solve the puzzle, then count the number of bends in each line. Answer U is the number for which the line joining them has Answer T bends.
- Slither Link -- Replace all 4 "U"s in the puzzle with the number from Answer U. Answer V is the total number of 1s inside the loop of the solved puzzle.
- Fillomino -- Replace "V" in the puzzle with the number from Answer V. Answer W is the number in the outlined cell of the solved puzzle.
- Heyawake -- Replace "W" in the puzzle with the number from Answer W. The final answer is the hiragana characters left white (not shaded black) in the solved puzzle, read from top to bottom and left to right.

Here I briefly describe how these 20 puzzles are connected so that you will (hopefully) be able to solve them all and get to the final answer. The basic procedure, after solving the first puzzle and answering a question about it, is to use the previous puzzle's answer to help solve the current puzzle and answer a question about the current puzzle, which gets used to solve the next puzzle, etc. As with my rules above, please let me know if there are any mistakes here. Having gotten this from computer translations with a bit of guess-work, things might not be completely right, but should still enable you to get through them all. Thanks!

- Ripple Effect -- Answer A is the number in the outlined cell of the solved puzzle.
- Nurikabe -- Replace "A" in the puzzle with the number from Answer A. Answer B is the shape of the island in the rightmost column containing the "4".
- LITS -- Answer C is the number of shaded tetrominoes in the puzzle of the same shape (in any rotation and/or reflection) as Answer B.
- Kakuro -- Answer D is the number of times Answer C's number appears in the solution.
- Akari -- Replace "D" in the puzzle with the number from Answer D and solve the puzzle.
- Masyu -- Copy the lights from Q5's solution into the grid as white circles and solve the puzzle. Answer E is how many cells in the column indicated by the arrow are empty (do not contain part of the line solving the puzzles).
- Heyawake -- Replace "E" in the puzzle with the number from Answer E. Answer F is the number of black cells in the column indicated by the arrow.
- Fillomino -- Replace "F" in the puzzle with the number from Answer F. Answer G is the number of 1s in the solved puzzle, including givens.
- Number Link -- Solve the puzzle treating the L, I, T, and S cells as empty cells. Answer H is the letter crossed by the line connecting the two numbers given by Answer G; if there are 2+ letters, the answer is the leftmost letter.
- LITS -- Answer J is the number of pieces with the same shape as Answer H, where all rotations and reflections of the shape count as the same shape
- Slither Link -- Answer K is the number of times Answer J appears inside the closed loop of the solved puzzle.
- Ripple Effect -- Replace "K" in the puzzle with the number from Answer K. Answer L is the number that appears the most in the row indicated by the arrow.
- Yajilin -- Replace "L" in the puzzle with the number from Answer L, and solve.
- Future steps still in progress -- I do hope to post this eventually, but it's not particularly high priority for me, and it will take some time to interpret the automatic computer translations when I do get around to it. Thank you for your patience.

The Nikoli books I own are (alphabetically):

- Penpa 2011-2017 (replaces the Penpa Mix series)
- Penpa Mix 1-6 (replaced with Penpa 20xx series)
- Puzzle Box 2-3, 6-12
- Puzzle Communication Nikoli 117-129, 131-156
- Puzzle Cyclopedia
- Puzzle the Giants Best Selection 1-2
- Slalom 1 [1]
- Tentai Show 1 [1]
- Yajilin 1 [1]

- Beyond Sudoku
- The Monster Book of Logic Puzzles & Sudoku (a collection of Nikoli-made puzzles, but the book's not published by Nikoli)
- The Ultimate 1001 Puzzle Book
- Yubotu

- Puzzle Box 1, 4-5, 13+
- Penpa 2018+
- Puzzle Communication Nikoli 130, 157+
- Marugoto series books
- Penpagon
- Camissimo (Nikoli original card game)

A few comments on the books: Puzzle Box is my favorite because it has the largest variety of puzzles that I can do. The quarterly Puzzle Communication Nikoli typically includes at least a few brand new types of puzzles, I'm guessing as tests to see what readers think of them. I think the best eventually go on to become regularly appearing puzzles. The Penpa books have the advantage of including rules in English, but often only have about a dozen different types of puzzles, so it's a bit low in variety. Most other books Nikoli releases seem to focus on one or a few specific puzzle types, except for the Puzzle the Giants series, which has a bunch of types but only large ones, frequently taking up a full page per puzzle. So no matter what your puzzle preferences are, Nikoli's probably got you covered. ;)

Footnotes:

**[1]** I selected these books as my prize for winning
Grant Fikes'
Attack of the Four Puzzles! contest.

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James Marshall (e-mail me)

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