How it works
Tap a peg to lift its top disc, tap another to put it down. Dragging was tried and
rejected: a disc half dropped between two pegs has nowhere to be, and this game is about
the decision rather than the hand.
Three discs take seven moves, four take fifteen, five take thirty-one, and the screen
says so. The Watch button plays the perfect answer, which is the recursion made
visible.