Torre di Hanoi. One disc at a time.

Choose a peg to lift its top disc, then choose the peg to set it down on. Only the top disc of a peg can move, and it may only be set on an empty peg or on a disc larger than itself. The board is finished when the discs stand in the arrangement drawn under it.

A tower of discs is a puzzle made of itself: to move the whole tower you must first move everything above the largest disc out of the way, which is the same puzzle one disc smaller. On three pegs that settles the fewest moves exactly — seven for three discs, fifteen for four, and double plus one for each disc after that.

A fourth peg breaks that rule rather than easing it. Eight discs take two hundred and fifty-five moves on three pegs and thirty-three on four, because somewhere below the largest disc the tower is split in two — and where to split it is the puzzle.

Nothing here can be lost. Every position has a legal move and every move can be taken back, so a board is never stuck and Reset is only ever a choice.

Tab reaches every peg; arrow keys move along the row, Enter or Space lifts a disc or sets it down, and Escape puts a lifted disc back. Undo takes back a move. Reset starts this board again; Next puzzle begins a new attempt on the next board.

Each board shows its par, the fewest moves it can be finished in. A finished board earns 100 points at par, less 5 for each extra move, down to 20. Undo takes back the board, never a move already counted, so the count you see is the count that is scored.

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