Evil Sudoku — Play Free Online

Evil is our hardest tier, tuned so that even strong pattern knowledge isn't enough on its own. Breakthroughs come from chain logic at full strength: nice loops that close a circuit of implications around the grid, and forcing chains that test a candidate by following every branch until all but one collapse.

Nothing here ever requires guessing — every Evil grid has a single solution reachable by pure logic — but the logic runs deep, and one puzzle can absorb an entire evening. If you finish one unaided, you've earned the right to be a little smug about it.

Treat evil as a destination rather than a daily diet. One or two grids a week, solved properly, will teach you more than a dozen abandoned halfway. And when you want to see the intended logic after conquering — or surrendering to — a grid, the solver can walk you through the next step of any position: a teacher, not a crutch.