Cube
Why does a blue face become blank in Cube?
Rolling swaps the colours of the touching floor square and solid face. A blue face touching a blank square deposits its colour. The goal is to hold every required blue face at once, not merely visit all blue squares.
Worked example
On the cube board, track which face will touch the next square before rolling. The colour is attached to the face, not to the direction of travel.
What to check on your board
Apply the rule above to your current board, then verify the remaining puzzle constraints. The example explains a local deduction; it is not a solution to every randomly generated board.
Checking your next move
Before rolling, identify the face that will touch the next floor square and note both colours. Apply that swap, then update the orientation of the solid. Keeping a tally of blue floor squares alone loses the information needed to know which faces are currently blue.
Using this reference
For Cube, read the rule and the worked example together before opening the game. Separate what the rule explicitly requires from what only seems likely on the current board. A useful next move is one you can explain from the visible constraints, not merely a pattern that looks familiar.
If you get stuck, isolate a smaller part of the position and list what is still possible there. After a move, check the affected rows, regions or connections again. The reference explains the documented rules; progress, controls and save behavior belong to the linked game.
Read the developer’s manual ↗ · Open the developer’s browser version ↗
Manual inspected: · Simon Tatham & contributors · MIT