Water Sort Puzzle
Pour liquids between bottles until each holds one color.
Play now →Sudoku
The classic logic puzzle, generated fresh every game with a guaranteed-unique solution and symmetric clues. Four difficulties, instant conflict highlighting, and your fastest times on record.
0s
Time
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Best
easy — fill every cell
Click a cell, then a number. Conflicts turn red instantly.
How to play
- Pick a difficulty — the board generates instantly with a unique solution.
- Click an empty cell, then a number on the pad (⌫ clears).
- Row, column and box conflicts turn red the moment they appear.
- Fill the whole grid correctly to stop the clock — fastest time wins.
Frequently asked questions
Is every puzzle guaranteed to have one solution?
Yes. Each board is generated by solving a random full grid and removing numbers in symmetric pairs, verifying after every removal that exactly one solution remains. You will never hit an ambiguous puzzle here.
What are the four difficulties?
Easy leaves 43 clues for a relaxed scan-and-fill, Medium 35, Hard 27, and Expert 23 — the point where advanced techniques like naked pairs and X-wings start earning their keep. Your fastest time per difficulty is saved locally.
How do I know if I made a mistake?
Conflicts light up instantly: any digit that repeats in its row, column, or box turns red. The Check button also counts wrong numbers — ones that differ from the unique solution — without revealing where to put the right ones.
Any tips for harder puzzles?
Scan for singles first, then box-line interactions. On Hard and Expert, pencil-mark candidates mentally and hunt for digits confined to one row or column of a box. If stuck, Check tells you how far off you are, not where to go.
Does sudoku really keep the brain sharp?
It is excellent focused practice for deductive reasoning and working memory within the game itself. Evidence that it broadly prevents cognitive decline is mixed — but as far as enjoyable logic workouts go, sudoku is the classic for a reason.