Fill every empty cell with a digit from 1 to 9 so that each row, each column, and each 3x3 box contains every digit exactly once. Pre-filled cells (shown in bold) cannot be changed. Conflicting cells are highlighted in red.

Controls

Key	Action
Arrow keys / WASD / hjkl	Move cursor
Mouse left-click	Focus a cell
`1`-`9`	Fill cell with digit
`Backspace`	Clear cell
`Ctrl+R`	Reset puzzle
`Ctrl+H`	Toggle full help
`Escape`	Return to main menu

Modes

Mode	Clues	Description
Beginner	45	Single Candidate / Scanning
Easy	38	Naked Singles
Medium	32	Hidden Pairs / Pointing
Hard	27	Box-Line Reduction / Triples
Expert	22	X-Wing / Y-Wing
Diabolical	17	Swordfish / XY-Chains

Quick Start

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