Three pegs and a stack of discs, biggest at the bottom. Move the whole stack to the right-hand peg — but you may only move one disc at a time, and a disc can never sit on a smaller one.
The secret is to think about the biggest disc first. To move it, every smaller disc has to be out of the way, stacked on the spare peg. So the job of moving five discs is really: move four out of the way, move the big one, then move the four back on top. That idea — solving a big problem with a smaller copy of itself — is called recursion.
Try the neighbours-only rules, where a disc can only move to the next peg, or a scrambled start where the discs begin spread across the pegs. The counter shows the fewest moves possible.
Move a stack of discs to the last peg, one at a time, never putting a bigger disc on a smaller one.
The full guide, with a worked example and common mistakes: How to play Disc Towers.
For the classic start, 2ⁿ − 1 moves for n discs. The counter shows the fewest for your position.
A disc can only move between neighbouring pegs (A↔B, B↔C), never straight from A to C. It takes many more moves.
Yes — Undo and Redo work for every move.