0 ⚡

The Orange Robot · Game 14

The Tower of Twenty-One

Twenty-one floors, and today only the top of the tower is unlocked to move. One key at a time. Never a bigger lock resting on a smaller one. Move the whole stack across, and the vault is yours.

This is a real Tower of Hanoi puzzle. It has a well-known optimal solution — the minimum number of moves for a stack of n disks is exactly 2ⁿ − 1. Every extra disk doubles the work, plus one more move. That's the same doubling math behind Bitcoin's halving schedule, and the reason the supply cap lands on 21 million instead of some round number — powers of two, not powers of ten.

Move one disk at a time — click a peg to lift its top disk, click another peg to place it.
Rule — a disk can never be placed on a smaller one.
Goal — move the entire stack to the third peg.