16
Lesson 16: Jellyfish
⏱ 30 minThe four-row extension of Swordfish. A digit in 2–4 cells across four rows aligning in the same four columns — eliminate from those columns.
Four-row fishColumn eliminationExtended pattern
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Expert Level
The final frontier. These techniques are used to crack the hardest puzzles in the world — reserved for the most dedicated solvers.
The Expert level is the pinnacle of the Sudoku Academy, designed for solvers who have completed the Advanced level and want to take on Evil Sudoku and other extreme-difficulty puzzles. Completing all 20 lessons will put you on a level with the best solvers on our leaderboard.
Lessons 16–20⏱ ~180 min total⚠ Challenging🆓 Free
Lesson List
17
Lesson 17: XY-Wing
⏱ 30 minThree cells forming a Y-shaped chain. The pivot cell shares one candidate with each wing — eliminate the shared candidate at the intersection of both wings' influence.
Y-wing pivotWing visibilityChain elimination
18
Lesson 18: XYZ-Wing
⏱ 35 minAn extension of XY-Wing where the pivot contains three candidates. All three cells (pivot and both wings) must see the elimination cell.
Three-candidate pivotTriple visibilityAdvanced wing
19
Lesson 19: Bowman's Bingo
⏱ 40 minA hypothesis-based technique: assume a candidate, propagate forced chains, and look for contradiction to eliminate it.
Hypothesis testingForced chainContradiction proof
20
Lesson 20: Advanced Chains (AICs)
⏱ 45 minMaster alternating inference chains (AICs) and discontinuous loops to handle the most diabolical Sudoku puzzles.
AIC chainsDiscontinuous loopsMaster strategy
Put these expert-level techniques to work on our most challenging puzzles — try an Evil Sudoku session and see how far these strategies take you. Track your progress and compete with top solvers on the global leaderboard.
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You've Reached the Top
Complete all 20 lessons to earn your Master Solver badge and unlock exclusive puzzles.
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