To solve a Chedoku puzzle
re-arrange the chess pieces to find a solution where the number of pieces threatening each square matches the
large number in that square.
White pieces add one to the threat count (+1), while black pieces reduce it by one (-1).
Can you remind me how the chess pieces move to threaten a square?
A pawn (♙) can capture an opponent's piece on a square diagonally in front of it by moving to that square.
pawns do not threat the quares in front of them
The king (♔) moves one square in any direction.
A rook (♖) can move any number of squares along a rank or file, but cannot leap over other pieces.
A bishop (♗) can move any number of squares diagonally, but cannot leap over other pieces.
A queen (♕) combines the power of a rook and bishop and can move any number of squares along a rank, file,
diagonal, but cannot leap over other pieces.
A knight (♘) moves to any of the closest squares that are not on the same rank, file, or diagonal. (Thus the
forms an "L"-shape: two squares vertically and one square horizontally, or two squares horizontally and one
vertically.) The knight is the only piece that can leap over other pieces.
Do I have to follow chess rules to move the pieces?
Chess rules are only used to calculate the threat numbers. You can move pieces freely and place them anywhere.
Chedoku puzzles can have several situations that you will never encounter in chess, for example:
any arbitrary number of pieces on the board, pawns in the first and last rows, missing king, missing opposite
Is there a limit in how many moves or how much time I can take?
There is no time limit, and you can move the pieces as many times as you want. Once you find a solution, the site
will show a notification displaying how many moves and how much time you took to find it.
Can I remove pieces or add extra pieces?
No, you cannot remove any pieces. You should find a solution only using the pieces already on the board.
Why can't I move the pieces off the board to start with a clean slate?
around (https://chessboardjs.com). If pieces are off the board, there is no
easy way to limit the number of pieces that you can add to the board. Finding a better solution is on my to-do
list. I would love to hear from you if you have any ideas on how to solve this!
What do the colours of the numbers mean?
The colours of the large numbers give you a hint how close you are to a solution. If the number turns green, it is
targeted by the correct number of pieces compared to the solution. If the number is targeted by fewer or more
pieces than required, the number turns more red for each missing or extra piece.
What is the difference between the big and the small numbers?
The large numbers show you the target threat of each square on the board that you need to find a solution. The
small numbers show the actual threat corresponding to the current configuration of pieces on the board. If you
want, you can turn off the display of the small numbers using the 'hint' setting.
What is the difference between a valid solution (yellow notification with ☑️ mark) and a perfect solution (green
notification with ✅ mark)?
Some puzzles can have more than one solution. If you find a solution where all the squares with large numbers are
threatened by the correct number of pieces, you found a valid solution. If some extra squares are threatened in
addition to the target squares, you receive a yellow notification with ☑️ mark. If all the squares with large numbers are
threatened by the correct number of pieces AND no additional squares are threated (i.e. the threat is zero for all
squares that do not have a number or a piece on it), you have found a perfect solution and will get a green
notification with ✅ mark. If you press the ‘solution’ button, you will see a perfect solution.
For example, in the puzzle below placing pawn on c2 is an imperfect solution but placing it on a2 is a perfect
In puzzles with black pieces, perfect solutions can be extra tricky to find, since the threats of white (+) and
black (-) pieces can cancel each other out, creating squares that look like there is no threat but that actually
require you to place two pieces threatening it to get to zero.
This was too easy, do you have more difficult puzzles?
In the Chedoku home page you can adjust the difficulty of the puzzles by using
slider on the top of the page. In general, puzzles with more pieces and puzzles that involve black pieces are more
This was too hard, do you have easier puzzles?
We recommend you start with the Tutorial and then move on to the
easier puzzles. In the Chedoku home page you can adjust the difficulty of the
using the slider on the top of the page. In general, puzzles with fewer pieces and puzzles that do not use the
black pieces are easier to solve.
We value your feedback and would love to hear your thoughts on the puzzle you just solved.
Please don't hesitate to reach out to us with any comments or suggestions.
You can contact us via email or through any of our social media channels.
💬 "Combining math and chess: new type of puzzle"
Dan Heisman, US Chess Federation National Master (NM) and a FIDE Candidate Master (CM).
💬 "Do you like Sudoku? Do you like chess? then you might like this - Chedoku! It's safer than Chess
- Adam Raoof, The Chess Circuit, The
Chess England, FIDE IA, IO and chess writer
💬 "I like it! Fun way to improve your understanding of the pieces' abilities." - Nathan Solon,
Chess master, Former poker pro, Data scientist
💬 "Nieuw soort schaakpuzzels, de chedoku! Wie sudoku's en schaakproblemen leuk vindt zal misschien in
chedoku een leuke combinatie van beiden vinden." - Nederlandse
bond van schaakprobleemvrienden,
Dutch association of chess problem friends
💬 "New find!! I'm being distracted by @chedoku puzzles when work starts soon! 🤩 My students will 🖤 these @ChessPlus
#visualisation #reasoning + & -" - hari_neo,
♟️Primary chess tutor 🦉Curious Maths teacher
💬 "Chedoku is exactly what it sounds like - Sudoku, but played with Chess pieces. It's a simple concept but it's been executed to perfection. Includes countless levels, each of which can be scaled up through 20 difficulty modes and there's also a daily puzzle. Countless hours of entertainment." - CSH Picone - Game Reviews,
Aussie game journo & Steam curator
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