Shuffle

the empty square is your only tool.

drag the hole around the tray until the ring closes

There is only one gap, and it is the only thing in the tray that can move. So push it: drag the hole, and each square it walks into ends up where the hole just was. That is the whole mechanism of a sliding puzzle, and it is why the tiles are never really what you are moving -- they are the wake the hole leaves behind it. The ring is broken wherever a tile is not home. It closes when the hole has walked every tile back into place and comes to rest in the middle.

Concepts: puzzles, logic.

An interactive you play with one thumb, on Wundr.