3Doku

About 3Doku

3Doku, by Andrew Taylor, takes classic sudoku and folds it onto a cube. The six faces are 4x4 grids, and the numbers run from 1 to 16 rather than 1 to 9. Each face must contain every number once, and so must each band of cells that runs across a face, over the edge and on around the cube until it comes back to where it started. Coloured bands in the display show these loops.

The hard part is keeping track of where a row goes when it turns a corner, since neighbouring faces are not always the same way up. The game helps: a highlighter shows every group a cell belongs to, pencil marks can be filled in automatically, and an auto-pencil removes candidates when you place a number. None of those count as hints. Highlighting errors or revealing cells does, and resets your streak.

There is one numbered puzzle a day, the same for everyone. Difficulty follows a weekly rhythm, easy on Monday and rising to Saturday, with Sunday a wildcard that is never too easy. A puzzle selector lets you go back to earlier days.

It suits sudoku players who have outgrown the 9x9 grid and want a spatial twist, and who are happy with a longer solve than most daily puzzles.

How to play 3Doku

1. Open 3Doku and start today's puzzle.
2. Turn the cube to see each face; every face needs the numbers 1 to 16.
3. Follow each coloured band over the edges and around the cube; it also needs each number once.
4. Use pencil marks and the highlighter to track candidates.
5. Fill every cell to finish, or pick an earlier puzzle from the list.

Tips

• Turn on automatic pencil marks; they do not count as a hint.
• Use the highlighter in groups-for-cell mode to see exactly which loops a cell is in.
• Start with the face that has the most givens and push numbers out along its bands.
• Expect the late-week puzzles to take much longer; save them for a free evening.

Questions