Tower of Hanoi

Tower of Hanoi is the classic mathematical puzzle with seven discs and three pegs. Click a peg to pick up its top disc, then click another peg to drop it — a larger disc may never rest on a smaller one. The selected peg lights up and the disc that will move lifts, so the state is always readable. Seven discs need at least 127 moves. Free, no sign-up, plays right in the browser.