How to play
Quick guide to rules, controls and modes.
Rules
Fill the 9×9 board with digits 1–9 so each row, column and 3×3 box has every digit exactly once. Every puzzle has one unique solution.
Controls
Click a cell, then type a digit. Shift+digit = note. Arrows move selection. Cmd/Ctrl+Z is undo. Esc deselects.
Modes
Classic for most, Paper for purists, Zen for relaxation. Toggle in settings.
Sudoku techniques
Naked single: cell with only one candidate. Hidden single: digit can go in only one spot in a row/column/box. Hint will explain it.