Expert Cube/3D Sudoku

A classic 9×9 grid folded onto the faces of a cube. Rows and columns wrap across face boundaries in three dimensions.

Easy Medium Hard Expert

Expert Cube Sudoku. Two interlocking expert grids with minimal givens — the deepest 3D spatial reasoning puzzle on the site.

Score
0
Mistakes
0/3
Time
00:00
Grid A
6
5
1
9
9
1
6
8
7
9
4
5
2
5
7
9
9
2
9
7
4
3
6
4
2
9
2
6
8
4
6
3
1
7
2
4
2
9
8
5
6
7
3
Grid A Shared Grid B
Grid B
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Expert · Cube/3D · 2 grids (153 cells)0%
How to play Cube/3D Sudoku
Two 9×9 Sudoku grids overlap at a shared 3×3 corner box. Grid A (blue tint) covers rows 1–9, columns 1–9. Grid B (green tint) covers rows 7–15, columns 7–15. The shared box (rows 7–9, cols 7–9) satisfies both grids. Each grid must independently satisfy standard Sudoku rules.
How to Play Cube / 3D Sudoku →

What is Cube / 3D Sudoku?

Difficulty
★★★★☆
4/5
Constraint Type
Twin Grids
Typical Givens
~30 per grid
Avg. Solve (Expert)
95 min

Solving Techniques for Expert Level

Technique Description Level
Shared Box Exploitation The overlapping 3×3 box satisfies both grids. Digits placed here eliminate from rows and columns in both Grid A and Grid B simultaneously. Beginner
Grid A/B Isolation Outside the shared box, each grid operates independently. Apply standard 9×9 Sudoku logic to each grid in turn. Intermediate
Cross-Grid Cascade Completing the shared box often cascades through the adjacent rows and columns of both grids, rapidly resolving nearby cells. Intermediate
Overlap Constraint The shared box must satisfy: Grid A's bottom-right box rules, AND Grid B's top-left box rules, AND both grids' overlapping row/column constraints. Advanced
Twin Digit Counting Each digit appears 9 times in Grid A and 9 times in Grid B, but only once in the shared box. This counting helps verify near-complete grids. Advanced

Average Solve Time by Difficulty

Easy
15 min
Medium
32 min
Hard
60 min
Expert
95 min
Want a full walkthrough of rules, strategies, and solving steps? How to Play Cube / 3D Sudoku →

Frequently Asked Questions — Expert Cube Sudoku

Is expert Cube Sudoku solvable without guessing?
Yes. Every expert Cube Sudoku on Sudoku.by has a unique solution reachable by logic alone. The dual-grid structure provides enough constraint overlap that advanced techniques — applied rigorously — always break deadlocks without the need for trial and error.
What advanced techniques are required for expert Cube Sudoku?
Expert puzzles require X-Wings and Swordfish patterns applied within individual grids, cross-grid naked and hidden sets in the shared region, and multi-step forcing chains that alternate between Grid A and Grid B. You must track the interaction of two complete Sudoku constraint systems rather than a single one.
How does 3D spatial reasoning help in expert Cube Sudoku?
Cube Sudoku's layout represents two overlapping puzzle planes sharing a corner. Thinking of the grids as two faces of a cube that meet at an edge helps you visualize which rows and columns are bridged by the shared region. Mentally rotating between the two grid perspectives — Grid A's view and Grid B's view of the shared cells — makes cross-grid deductions more intuitive.
How many cells does an expert Cube Sudoku have and how does this affect difficulty?
Cube Sudoku has 153 active cells — 162 from two 9x9 grids minus 27 shared cells counted only once. The larger count means more total work, but more importantly it means more constraint interactions. Expert puzzles exploit this density to create situations where you must track four or five units simultaneously before any single placement becomes provable.
How long does an expert Cube Sudoku take?
Expert Cube Sudoku puzzles take most players 75 to 120 minutes. The combined scope of two interlocking grids with expert-level constraint density requires sustained concentration. If you are stuck for more than 25 minutes, systematically apply X-Wing searches within each grid separately, then check whether any candidate remaining in the shared region allows a cross-grid locked-candidate elimination.

More questions? See the full Cube Sudoku guide.