About 3D Sudoku
The Concept: This puzzle expands standard Sudoku into a 9x9x9 matrix. Every single layer across all three dimensions (X, Y, and Z) is a complete, interlocking 9x9 Sudoku puzzle, creating 27 simultaneous games.
The Masking Effect: If you solve the outer faces (Planes 1 and 9) first, they form a solid shell that hides the inner cubes. To prevent this, completed outer planes turn a lighter, translucent green, allowing you to see inside.
Auto-Save & Resuming: Your progress is automatically saved by your browser in the background. You can return later and click RESUME GAME to pick up exactly where you left off. Note: Depending on your browser, this automatic resume feature may not carry over to Incognito or Private browsing windows. For a permanent, shareable backup of your 3D puzzle, use the manual EXPORT and IMPORT buttons.
The Math: Generating these puzzles relies on the Exact Cover problem. For a standard grid, letting Xi,j,k = 1 if digit k is in row i, col j, the algorithm satisfies four constraint groups. For example, the row constraint is:
Σ(j=1 to 9) Xi,j,k = 1
This is calculated across all intersecting 3D planes simultaneously.
Fun Fact: The name "Sudoku" is a Japanese abbreviation of the phrase "Sūji wa dokushin ni kagiru", which translates to: "the digits must remain single."