Our mission
PuzzleShikaku exists to be the best place on the web to play and learn Shikaku: a clean, fast board that feels good on every device, puzzles you can trust, and guides that actually teach you to solve.
How our puzzles are made
- The generator randomly divides the grid into rectangles, favouring interesting shapes and avoiding long thin slivers.
- It places one number inside each rectangle. On easy puzzles numbers tend to sit at corners, which narrows the options; on hard puzzles they sit anywhere.
- A solver checks the result. If the puzzle has more than one solution, the numbers that caused the ambiguity are moved and the check runs again; puzzles that cannot be fixed are thrown away.
Each puzzle is generated from a numeric seed — the puzzle ID shown beside the board — so the same ID always produces the same grid. That is how shared links and the daily, weekly and monthly challenges work.
Unique solutions, guaranteed
The solver searches exhaustively and stops only after proving there is exactly one way to complete the grid. You never need to guess.
Difficulty grading
Instead of judging difficulty by size alone, we measure which techniques a puzzle needs. Easy puzzles must be solvable using only forced options and reachability; Medium puzzles add overlap reasoning; Hard puzzles require deeper chains. See the strategy guide for details.
Privacy
No account is needed. Progress, settings and statistics are stored in your own browser. We use Google Analytics for Firebase to understand overall usage — see our privacy policy.