How the swap puzzle works
Unlike a slide puzzle, any tile can trade places with any other. Drag a tile onto the one you want to swap it with, or tap one tile and then the other. A tile that arrives at its correct position gets a thin green outline and locks, so you cannot move it out by accident.
The board uses square tiles, so a wide picture gives more columns than rows: 5 columns make a 5 × 3 board, 8 columns make 8 × 5. The picture is cropped slightly at the sides to fit.
How few swaps can it take?
On a board with N tiles you never need more than N − 1 swaps. The trick is to make every swap count: move a tile directly to its home spot, and the tile you take out of that spot is now the next one to place. Following such a chain fixes one tile per swap, and the very last swap of a chain fixes two.
If you want to count, the move counter is there, and your best move count for each size is saved.
A reliable order of work
Start with tiles that carry something unmistakable: an eye, a fin, a mast, the edge of a shell. Look at the preview, find where that detail lives, and swap the tile straight there. Corners and edges come next, because the outline of the picture is easy to read. Plain tiles of open water or sand are easiest at the end, when only a few spots remain.
Stuck? The hint button highlights a pair of tiles that can be swapped to put at least one of them right.
Sizes
3 × 2 and 4 × 3 are quick, relaxed puzzles for a few minutes. 5 × 3 and 6 × 4 are the middle ground. 7 × 5 and 8 × 5 put 35 and 40 tiles on the board — on a phone the tiles get small, so turning the phone sideways helps.
Questions
Why do some tiles stop moving?
A tile in its correct place locks so it cannot be swapped away by mistake. It is your sign of progress.
Do I have to drag?
No. Tapping one tile and then another swaps them too, which is easier on small screens.
Is a swap puzzle always solvable?
Yes. Swaps can untangle any mix of tiles, so no deal is impossible.
Why is the picture cropped?
The tiles are square, so the picture is trimmed a little at the sides to fit a whole number of tiles.