🗼 Tower of Hanoi

How to play

Every disk starts stacked on Tower 1, largest at the bottom, and the puzzle is solved when the whole stack sits on Tower 3 in the same order. You move one disk at a time, always the top one, and a disk may never rest on a smaller disk. A move is two clicks: one on the tower you take from, one on the tower you place on.

• Tower area — click or tap a tower to pick up its top disk, then click another tower to drop it. Clicking the selected tower again cancels the pick-up.
• 3 Disks, 4 Disks, 5 Disks buttons — restart with that many disks.
• Reset button — returns every disk to Tower 1 and clears the move counter, keeping the current disk count.

Scoring

There are no points, only a move counter and the theoretical minimum beside it: two to the power of the disk count, minus one, which is 7 moves for 3 disks, 15 for 4 and 31 for 5. Every accepted move adds one. An illegal move is refused with a message and cancels the pick-up without costing a move, and clicking an empty tower with nothing selected does nothing.

Tips

• Think recursively: to move n disks to Tower 3, move the top n-1 to the spare tower, move the largest across, then bring the n-1 back on top.
• Parity shortcut: with an odd number of disks send the smallest to Tower 3 first, with an even number send it to Tower 2.
• Never move the same disk twice in a row. Every other move is the smallest disk, and between those there is only one legal alternative.
• Learn the seven move pattern on 3 disks first. The 4 and 5 disk solutions are that pattern wrapped around itself.

Frequently asked questions