Hexadoku Expert Online: Fish Patterns at Maximum Scale

Hexadoku Expert is an advanced 16×16 logic puzzle played with sixteen symbols — digits 1–9 and letters A through G — across 256 cells. Expert puzzles begin with 62–74 starting clues. At this level, the fish pattern family becomes essential: X-Wing, Swordfish, and Jellyfish appear throughout the grid, and the Squirmbag — a five-row fish pattern rarely practical in smaller grids — begins to matter. Play free at SudokuPro — no registration required.

Characteristics of Hexadoku Expert

• Grid: 16×16 = 256 cells
• Symbol pool: Digits 1–9 plus letters A–G
• Starting clues: 62–74
• Logic required: X-Wing, Swordfish, Jellyfish, first Squirmbag patterns
• Typical solve time: 90–150 minutes
• Best for: Experienced solvers who have mastered pairs and locked candidates

Expert is where Hexadoku's scale becomes an advantage for advanced solvers. Fish patterns that are rare in 9×9 Sudoku appear more frequently because the 16×16 grid creates more possible row and column combinations.

Solving Strategies for Hexadoku Expert

Strategy 1: X-Wing and Swordfish

Fish patterns eliminate candidates by exploiting repeated confinement across rows and columns. An X-Wing occurs when two rows restrict a symbol to the same two columns. That symbol can then be eliminated from other cells in those columns.

Swordfish extends the same idea to three rows and three columns. In Hexadoku, these patterns appear more often because there are sixteen rows and sixteen columns to combine. The key is systematic scanning: for each symbol, identify rows where candidates are limited to two or three columns, then check whether those columns align with other rows.

Strategy 2: Jellyfish

Jellyfish extends fish logic to four rows and four columns. If a symbol is confined to the same four columns across four rows, it can be eliminated from those columns in all other rows.

In classic Sudoku, Jellyfish is relatively rare. In Hexadoku, the wider grid makes it a practical Expert-level technique. Complete and accurate pencil marks are essential; one missed candidate can hide the pattern or create a false one.

Strategy 3: First Squirmbag Patterns

A Squirmbag, also called Starfish, is a five-row fish pattern confined to five columns. It is too rare to hunt regularly in many 9×9 puzzles, but in Hexadoku it becomes realistic because the grid has sixteen rows and columns.

At Expert level, Squirmbag often appears in partial or early forms. Recognizing these formations prepares you for Hexadoku Extreme, where full Squirmbag eliminations become part of the normal solving toolkit.

Next Steps

Ready for deeper chains? Advance to Hexadoku Extreme, where XYZ-Wing, full Squirmbag patterns, and 12–18-link AIC chains define the solving space. Return to Hexadoku Hard to consolidate pairs logic, or visit the Hexadoku hub for a full level overview. For the final 16×16 challenge, continue to Hexadoku Evil.