Play Evil Sudoku Online - Free
Evil Sudoku is the hardest bucket in our library - the level apps variously call evil, insane or diabolical. Solving one usually takes chain-based reasoning: X-Chains, XY-Chains and forcing chains that track what happens if a candidate is true or false across many cells. It is slow, it is humbling, and finishing one without hints is a genuine achievement. Our coach-style hints can walk you through any stuck point step by step, teaching the pattern instead of just revealing the answer.
Techniques you'll need
- X-ChainWhen one digit travels through alternating strong and weak links.
- XY-ChainWhen two-candidate cells form a forcing chain.
- Forcing ChainWhen every candidate of one cell forces the same conclusion.