Evil sudoku grids with 22 to 25 clues and one solution each. They are rated as beyond Expert: somewhere in the solve you need a forcing chain, and very rarely trial and error. For solvers who know their X-wings. No app, no sign-up, no interstitial before you play; works offline and with the keyboard.
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An Evil grid needs everything from Easy to Expert and then at least one step that no pattern covers. The rater uses a forcing chain for that step.
Choose a cell with exactly two candidates, say 3 and 9. Assume it is 3 and follow the consequences: each forced single, then the singles those create. If the chain ends in a contradiction, such as a cell with no candidates left or a digit repeated in a unit, then 3 was wrong and the cell is 9.
Pick two-candidate cells whose digits have few options elsewhere, and cells that see many other two-candidate cells. A chain without a contradiction proves nothing; try another cell.
Here you can place the assumed digit, follow the singles and, if it breaks, undo back to where you started. Undo covers the whole game. The mistakes counter records a wrong placement as you enter it, so turn the counter off in settings if you prefer to test freely.
For the rare grid that needs more than a short chain, the hint says Guess and places the correct digit.
The timer starts on your first move and pauses when you switch tabs. Evil stats stay in your browser: played, won, win rate, best and average time. Undo and redo cover the whole game. The first two hints per puzzle are free; later hints may offer a short ad or a 30-second wait. A puzzle code such as A7K3Q (?p= in the address) replays the same grid, and the win panel gives a result to share.
Evil grids also print as PDFs.
Evil sudoku runs on a phone as well as a desktop, and undo makes testing a chain painless from either touch or keyboard. Tidy Puzzles runs entirely in your browser: there is no app to install, no account to create and no interstitial before you can play. After the first visit the game also works offline, because each puzzle is generated on your device from a seed. Every board can be played with the keyboard alone, on a phone or a desktop, and your stats and unfinished puzzles stay in this browser rather than on a server.
Evil is the hardest here: 22 to 25 clues and at least one step that needs a forcing chain.
Between 22 and 25, though the techniques needed matter more than the count.
Yes. Every grid is checked by a solver that counts solutions and stops if it finds a second one.
Nothing forbids it, but a forcing chain is a guess followed to a contradiction, which proves the answer.
A name some publishers use for their hardest grade. It roughly matches Evil here: beyond X-wings and swordfish.
All five levels, the daily, kids grids, printables and the solver.
24 to 27 clues, adds X-wing, Y-wing and swordfish.
26 to 30 clues, adds pairs, triples and box-line reduction.
One grid a day for everyone, Hard by default, with streaks.
Solve, check or step through any grid you type in.
Evil grids as a PDF, with solutions at the end.
Sums instead of rows: the crossword cousin of sudoku.
Logic on a hidden board, with a safe first click.
Last updated 2026-09-27. Written and maintained by the Tidy Puzzles team; puzzles are generated on your device. How it works.