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Guidebook · Stage 03

Advanced Sudoku Techniques

When singles stall, lean on structure: locked candidates, fish patterns, chains, and coloring to keep progress calm and logical.

Difficulty: Hard+ Updated monthly Read time: ~6–10 mins each
Geometric stones and a Sudoku notebook for advanced lessons
01 Foundations02 Candidate tools03 Advanced patterns

Read the structure

Advanced patterns

Use these lessons when the next move is an elimination rather than a placement.

pointing pairs triples locked candidates type 1 Sudoku technique diagram

Elimination

Pointing Pairs / Triples

Lock candidates within a box to clear rows/columns and open new singles.

5 min readHard
box line reduction locked candidates type 2 Sudoku technique diagram

Elimination

Box–Line Reduction

Use line-locked candidates to thin boxes and reveal follow-up singles.

5 min readHard
x wing Sudoku technique diagram

Pattern

X-Wing

Spot two-line fish to wipe out candidate clutter before resorting to chains.

6 min readHard
swordfish Sudoku technique diagram

Pattern

Swordfish

Scale the X-Wing idea to three lines for tougher grids that resist basics.

7 min readHard
jellyfish Sudoku technique diagram

Pattern

Jellyfish

Four-line fish for extreme cases—use sparingly when other patterns fail.

8 min readExpert
xy wing Sudoku technique diagram

Chains

XY-Wing

Pivot on a hinge cell to eliminate a shared candidate across two wings.

6 min readHard
xyz wing Sudoku technique diagram

Chains

XYZ-Wing

Add a third candidate to force a single elimination from the hinge cell.

6 min readHard
w wing Sudoku technique diagram

Chains

W-Wing

Pair two bivalue cells with the same digits and a linking conjugate pair.

6 min readHard
alternating inference chains aics Sudoku technique diagram

Chains

AICs & Forcing Chains

Alternate strong/weak links to drive eliminations without guessing.

8 min readExpert
coloring Sudoku technique diagram

Logic

Coloring & Multi-Coloring

Track conjugate pairs with colors to prove contradictions and force placements.

7 min readExpert
uniqueness techniques unique rectangle etc Sudoku technique diagram

Uniqueness

Unique Rectangles

Prevent deadly patterns by eliminating candidates that would create multiple solutions.

6 min readHard
fish variants finned x wing sashimi etc Sudoku technique diagram

Variants

Finned & Sashimi Fish

Handle imperfect fish shapes by checking fin positions for targeted clears.

7 min readExpert
als techniques als xz als chains Sudoku technique diagram

ALS

Almost Locked Sets

Use near-complete sets to create strong/weak links and chain into eliminations.

9 min readExpert
sue de coq Sudoku technique diagram

Hybrid

Sue de Coq

Combine row, column, and box logic to lock down complex candidate groups.

9 min readExpert