9️⃣ Sudoku
🧩 Logic · 0 playsSudoku
Place one to nine in every row, column and box, using logic alone.
About Sudoku
Nine rows, nine columns and nine boxes, each of which must hold the digits one to nine exactly once. No arithmetic is involved — every placement follows from what the surrounding cells forbid. Boards are generated with a single solution and graded across four levels, so the same reasoning carries from a gentle grid through to an expert one. Pencil notes allow candidates to be recorded while a longer chain of deduction is worked out, and a timer is there for anyone who wants the pressure.
How to Play
Select an empty cell, then choose a digit to enter it. Each row, each column and each three-by-three box holds the digits one to nine without repetition. Switch to notes mode to record candidate digits before committing to one.
💡 Tips & Strategy
Scanning beats guessing, and it solves most gentle grids on its own. Take a digit that already appears five or six times and trace its rows and columns across the boxes it is missing from; often a single cell survives. Work one digit at a time, all the way from 1 to 9, before you reach for anything more sophisticated.
When scanning dries up, count instead. Any row, column or box holding just two or three gaps is nearly forced: list what is missing and test each candidate against the other two units it belongs to. The answer is usually compelled rather than chosen.
Harder grids need pencil marks, and two patterns repay the effort. A hidden single is a candidate that survives in only one cell of a unit, even where that cell holds several other options — this is the most common breakthrough on a stuck grid. A naked pair is two cells in one unit sharing the same two candidates; whatever else happens, those two digits live there, so strike them from every other cell in the unit.
A properly made puzzle never requires a guess, and every grid here is generated with exactly one solution. If you are tempted to guess, the deduction you have missed is nearly always a simple one a few units away.