Bring the marble out through the double ring.
Drag the cube to turn a layer, or swipe beside it to roll the whole cube.
Drag with two fingers (or right-drag) to look around; pinch or scroll to zoom.
More controls
The marble falls straight down after every move and leaves only when the double ring faces down. The top line shows the board, then moves made and par.
Hint shows a next move; press it again to play it.
The arrow keys roll the cube toward that side of the screen. F, B, L, R, U and D turn the front, back, left, right, top and bottom layers; on a three-cubie cube M, C and S turn the middle ones. Shift turns the other way. Q and E turn the view, + and − zoom, and 0 resets it. Z or Backspace undoes; H asks for a hint.