Puzzles2 min read

How to play Sudoku

Fill a 9×9 grid with the digits 1 to 9 so no digit repeats in any row, column or 3×3 box.

Goal

Complete the grid so every row, every column and every 3×3 box holds each digit from 1 to 9 exactly once.

Some digits are given at the start. They can't be changed.
Pick an empty cell, then pick a digit (or type it). Pick the same digit again, or Erase, to clear the cell.
Switch to Notes to jot down the digits a cell could still be. Notes are reminders only and are never checked.
A digit that repeats in its row, column or box turns red straight away.
The puzzle is solved the moment the last cell is filled correctly. Every puzzle has exactly one solution.

If row 1 already has 1 to 8 in it, the one empty cell in row 1 must be 9.

Keys	What it does
`1–9`	Put that digit in the selected cell (or note it, in Notes)
`←↑→↓`	Move around the grid
`Backspace`	Clear the selected cell
`N`	Switch between digits and notes

Take one digit at a time and look for the single place it can go in each box.
Look for a cell where eight digits are already used by its row, column and box. The ninth must go there.
Easy and Medium puzzles never need anything harder than those two steps. Hard and Expert ones need notes.
On Easy and Medium, a hint fills in one cell.

Every correct answer is worth 100 points, scaled by difficulty (Easy ×0.8, Medium ×1, Hard ×1.3, Expert ×1.6).
Answering within 3 seconds adds a 25-point speed bonus.
Each answer in a row adds a 15-point streak bonus, up to 10 in a row.
Using a hint halves the points for that answer and skips the bonuses. Hints are only available on Easy and Medium.
Your score, streak and achievements are saved to your account when the game ends.

Classic

A fixed number of rounds, then a results screen.

Endless

Keep playing until you press Quit.

Time Attack

Fit in as many rounds as you can before the clock runs out.

Survival

Play until you run out of lives or make the game-ending mistake.