Extreme sudoku
Extreme sudoku is solved with chains: links of notes that prove one of two ends is true. Hard, but never a guess: every puzzle here can be solved by logic alone.
A thousand Extreme puzzles, free in your browser. No sign-up, nothing to download.
What it takes
How often each technique is needed in the game’s Extreme puzzles, counted over 300 of them:
- Hidden singlesin 100% of them
- Locked candidatesin 99% of them
- Naked singlesin 86% of them
- Pairsin 82% of them
- Mixed chains (AIC)in 78% of them
- Skyscraper and 2-String Kitein 72% of them
- XY-Chainin 68% of them
- W-Wingin 42% of them
- XY-Wingin 39% of them
- X-Chainin 29% of them
- XYZ-Wingin 27% of them
- Triplesin 25% of them
- X-Wingin 23% of them
- Swordfishin 3% of them
- Quadsin 1% of them
- Jellyfishrarely
Extreme puzzles start with 22 to 28 digits given, 25 on average. Every one has exactly one solution, and none needs a guess.
Tips
- Start a chain from a note you’d like to remove, and look for strong links on both sides of it.
- Keep chains short: the shortest one that works is the one to look for.
- A cell with two notes is a strong link of its own: chains can hop through it.
Other levels
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