Stack Sort

Stack Sort is a free online disc-stacking puzzle you can play instantly in your browser, no download or account needed. Tap a peg to lift its top disc, then tap another peg to place it — a disc can only land on an empty peg or on top of a disc that's strictly larger than it, so every move takes real planning. Unlike a simple pour-and-match sort, size matters here as much as color: it's a colored twist on the classic Tower of Hanoi. Play through 15 levels that add more colors, taller stacks, and fewer empty pegs as you climb, with no timer forcing you to wait between rounds — clear a level and the next one unlocks immediately. Undo mistakes, use a limited hint when you get stuck, and replay any unlocked level for a fresh layout.

How to play Stack Sort

1. Tap a peg to lift the disc sitting on top of it.
2. Tap a second peg to place it there — this only works if that peg is empty or its top disc is larger than the one you're moving.
3. Color doesn't affect where a disc can land, only whether a peg counts as finished, so plan a few moves ahead.
4. Sort every peg into a single color (or empty) to clear the level and unlock the next one.
5. Levels get harder as you go: more colors, taller stacks, and fewer empty pegs to work with.

Tips

• Keep at least one peg empty as long as possible — it's your only free workspace for untangling a mixed stack.
• Small discs are easy to move almost anywhere; save your empty pegs for relocating the big ones.
• Look for a color that's already mostly stacked in size order and finish it first to free up space.
• Stuck? Use Undo to back out of a bad move, or spend a hint to see a move that helps.

FAQ