🔢 Sudoku
Fill the grid so every row, column and box holds one to nine. Pencil marks included.
LEVEL
TIME 0BEST 0LEFT 0ERRORS 0
How to play Sudoku
- Choose a difficulty and press Start to generate a fresh puzzle.
- Select an empty cell, then type or tap a digit from one to nine.
- Every row, every column and every three-by-three box must contain each digit exactly once.
- Switch to Notes mode to pencil in candidates without committing to an answer.
Controls
| Input | Action |
|---|---|
| Click / tap | Select a cell |
| 1–9 | Enter a digit |
| Backspace or 0 | Clear the cell |
| Arrow keys | Move between cells |
| N | Toggle notes mode |
| H | Reveal one cell as a hint |
| Ctrl+F | Enter or leave full screen |
| Esc | Leave full screen |
Tips & strategy
- Scan for the digit that already appears most often on the board — it is usually the easiest one to place next.
- If a row has only one empty cell left, fill it immediately. These cascade.
- Use notes on Hard. Trying to hold six candidate sets in your head is how mistakes creep in.
- The conflict highlight shows clashes instantly, so if a cell turns red, undo before building on top of the error.
Frequently asked questions
Does every puzzle have exactly one solution?
Yes. Puzzles are generated by removing clues only while a unique solution can still be proven, so no guessing is ever required.
What is the difference between the difficulties?
Easy leaves around forty clues, Medium around thirty-two, and Hard around twenty-six. Fewer clues means longer chains of deduction.
Do hints count against me?
Each hint reveals one correct cell and adds thirty seconds to your finishing time, so a hinted solve will not beat a clean one.