Sidle: Sliding Puzzle

Classic slide puzzle. One empty square, tap a neighbour, sort every row.

One square is empty, and that emptiness is the only tool you have. Tap a tile beside it and the tile slides over. Everything else waits.

The target is not a picture but a rule: each row wants one kind of tile. Tiles read by shape and by the number of rings nested inside them, so nothing here depends on telling two colours apart.

Every board is scrambled by sliding backwards from a finished one, so it is always solvable. The parity trap that makes some sliding puzzles impossible cannot occur. The "best" count is the true minimum, proved by search rather than assumed from the scramble.

No timer and no lives. The one limit is a generous move budget - five times the shortest solution found by search, and never under 20 - shown as you play. A small key under the board shows what finished looks like.