A Soma style cube puzzle app for iPhone
Connected cube pieces, one box, and one rule: fill it exactly. Cubo keeps the mechanic that makes a Soma cube worth owning and drops the part where a piece rolls under the sofa.
Free on iPhone.
What carries over from the classic puzzle
The classic Soma cube is a set of seven pieces built from unit cubes that assemble into a three by three by three cube. Cubo keeps the three things that make that puzzle work:
- Every piece is connected. A piece is a group of cubes joined face to face, never a loose scatter of cells.
- The fit has to be exact. No gaps left over, no piece overlapping another, no piece hanging outside the box.
- Rotation in three dimensions is the difficulty. Seeing that a shape becomes the missing shape once you turn it is the whole puzzle.
Where Cubo leaves the classic set
Cubo does not reproduce the seven piece three by three by three set. It builds a new piece set for every round by taking a filled box and cutting it into connected regions. That has two consequences worth knowing before you download it:
- The pieces are not a fixed cast you learn by name. They change from board to board.
- The box is not always a cube. Two of the three difficulties are flat or two layers deep rather than equal on all sides.
The piece sets Cubo generates
| Difficulty | Box | Cells to fill | Pieces | Cubes per piece |
|---|---|---|---|---|
| Easy | 4 by 4 by 1 | 16 | 4 | 3 to 5 |
| Medium | 4 by 4 by 2 | 32 | 6 | 4 to 6 |
| Hard | 5 by 5 by 2 | 50 | 8 | 5 to 7 |
Easy is a single layer, so it plays as a flat shape fitting puzzle. Medium and Hard are two layers deep, which is where a piece can only go in if you turn it out of the plane.
What an app gives you that a wooden set does not
- A restart button. The arrow at the top right rebuilds the board instead of you tipping the pieces out.
- A timer, if you want one. Speed mode records a best time for each difficulty separately.
- A new set every round, plus one board a day that is the same for every player.
- Placement that cannot go wrong by accident: the arrows step only through positions where the piece genuinely fits.
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Questions about the pieces
Is Cubo a Soma cube app?
Cubo is Soma style rather than a reproduction. It shares the mechanic, which is fitting connected cube pieces into a box with no gaps and no overlaps, but it does not ship the classic seven piece set for a three by three by three cube. It generates its own piece sets instead.
Are the pieces always the same?
No. Each round the game cuts a fresh box into connected pieces, so the shapes you get change from board to board. The number of pieces and the size range they fall into are fixed per difficulty.
Can a generated board be unsolvable?
No. A board is made by taking a completely filled box and splitting it into connected regions, so a solution exists by construction: the arrangement it was cut from. There may be more than one.
How many ways can a piece be turned?
A polycube has at most 24 rotations in three dimensions. Cubo computes the distinct ones for the selected piece and the Rotate button cycles through exactly those, so a symmetric piece has fewer steps rather than repeated ones.
Is there a solver or a hint button?
No solver and no hint that finishes the board for you. The one line of text above the controls tells you which control to reach for, and the position arrows only offer legal placements, but the arrangement is yours to find.
Get a fresh piece set