Each board is one continuous gradient cut into tiles and shuffled. The pinned tiles never move and the corners are what fix the gradient, so every other tile has exactly one place it belongs — you are reading the board, not guessing at it.

Drag a tile onto another to trade them, or tap one tile and then a second. Par is the fewest swaps that can finish the board, and it is computed rather than estimated, so it is a target you can actually beat instead of a grade.

Choose Easy, Medium, or Hard for 5×4, 7×5, and 9×6 boards, take a hint that is always an optimal swap, and keep personal best and average times for every difficulty. Colours are generated in OKLab, so an equal step in the gradient looks like an equal step.

No board is ever shown unless it stays readable with red and green removed, and a colour-blind palette option in Settings raises that floor further.