Sudoku
Controls
About this game
Sudoku is the modern logic puzzle that quietly took over commute trains and waiting rooms worldwide. Our lithappy edition gives you three difficulty levels with progressively more empty cells - Easy fills in plenty of starting numbers for a relaxing solve, Medium offers a satisfying mid-week challenge, and Hard digs more than fifty cells out and demands genuine planning. Every board our generator produces is guaranteed to have exactly one valid solution, verified by an internal solver before it ever reaches you, so you never waste time on an ambiguous puzzle. A live timer tracks your run and your personal best for each difficulty is saved between sessions, with the timer pausing whenever you switch tabs so background time never sneaks into your record. Misplacements are highlighted in red the moment you make them, but the game never locks you out - feel free to experiment, undo, and try again. Polished, quiet, and just hard enough to make you feel sharp.
Tips & tricks
- Look for the row, column or 3x3 box that already has the most numbers - one or two missing slots are easy to resolve.
- Practice cross-hatching: cover the box, then scan the rows and columns intersecting it to see where a digit must go.
- If you're stuck, switch attention to a different number entirely - placing one new 5 often opens fresh constraints elsewhere.
- Use erase liberally - it's better to clear a guess than carry an error that breaks later deductions.
- On Hard, write down candidate numbers mentally one box at a time; trying to solve the whole grid in your head burns out fast.
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