Extreme Sudoku

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Extreme Sudoku - The Ultimate Logical Challenge

Extreme is the pinnacle of human Sudoku solving. Every advanced technique must be available to you. Some puzzles will require multi-step chains where a single missed candidate invalidates an hour of work.

What Makes a Puzzle Extreme?

An Extreme puzzle is constructed with as few given cells as possible - Typically 17–22 - While maintaining a unique solution. This means the solver must make every deduction count. Unlike Master level, where you can often reach a breakthrough with established techniques, Extreme frequently requires advanced chain logic and multi-technique sequences.

Complete Technique Reference

Technique	Difficulty	Purpose
Singles (Naked + Hidden)	★	Foundation - Direct placements
Pairs / Triples / Quads	★★	Candidate elimination in units
Pointing / Box Reduction	★★	Cross-unit elimination
X-Wing / Swordfish / Jellyfish	★★★	Fish eliminations across 2–4 rows
XY-Wing / XYZ-Wing / WXYZ-Wing	★★★	Pivot-pincer eliminations
Simple / Multi Colouring	★★★★	Chain-based contradiction chains
Finned / Sashimi X-Wing	★★★★	Extended fish with partial base
Alternating Inference Chains (AIC)	★★★★★	Generalised strong/weak link chains
Almost Locked Sets (ALS)	★★★★★	Complex candidate network logic

Your Path to Extreme Mastery

Confirm Master fluency - If Hard or Expert puzzles still occasionally stump you, return there first.
Learn Jellyfish - The 4×4 extension of X-Wing/Swordfish. Rare, but Extreme puzzles sometimes require it.
Study AIC (Alternating Inference Chains) - The single most powerful technique below trial-and-error. An AIC treats the grid as a network of implications; it generalises colouring, X-Wing and almost everything else.
Practice ALS logic - Almost Locked Sets allow eliminations that no standard technique can produce. These appear in the most diabolical Extreme puzzles.
Build endurance - A single Extreme puzzle may require over 100 deliberate deductions. Concentration matters as much as technique knowledge.
Join the community - Use the weekly tournament and global leaderboard to benchmark your progress.

World-Class Solving Times

Extreme solving time ranges by player tier:

Expert completing first Extreme 90–180+ min

Experienced Extreme solver 60–120 min

Tournament-level player 35–70 min

Elite competitive solver 20–40 min

World-class (sub-30 min) < 30 min

Extreme Community Stats

Metric	Stat
% of players who attempt Extreme	15%
% of Extreme attempts completed	41%
Avg hints used per completed game	1.8
Avg given cells	17–22
Techniques typically needed per solve	5–9
Median solve time (completions only)	78 min

Quick Facts - Extreme Sudoku

Given cells	17–22 out of 81
Techniques required	All of them
Notes mode	Non-negotiable
Avg solve time	60–120+ minutes
Completed by	~6% of players
Previous level	Master
Leaderboard	Global Rankings →