Spectrum Sort

Ten bottles, every one of them holding something. Four colors jumbled through the lot, and a single empty vessel to your name: the tall spare on the right.

Tap a bottle to pick it up, tap another to pour. Liquid only ever lands on its own color or into an empty bottle, and the whole matching run on top travels at once — as much of it as will fit. Get every bottle down to a single color and the level is done.

The spare takes a single color, twelve layers deep, which is enough to park an entire hue while you dig out what is underneath it. Nothing on the shelf starts empty, so at first it is very nearly the only room you have. Treat it as a loan rather than a solution: the level will not count as solved until you have emptied it again.

Every few levels the shelf gets harder in four directions at once. Another color joins. The bottles get a layer deeper. A couple more appear. And the buffer loses two of its layers — down and down, until somewhere around level twenty-one it is gone completely and you are sorting seven colors with nothing but the board itself.

Every board is checked by a solver before you ever see it, so a level that looks impossible never is. There is a target move count to beat for three stars, unlimited undo when a line goes wrong, and your progress is saved at the end of each level, so you can leave mid-shelf and pick it up later.