Below the picture are columns of boxes. Each box has a color and a number. Tap one and it moves into a free slot, and that many ants of that color march out. Each ant picks up one block of its color and carries it to the anthill.
Ants can only take the blocks they can reach, and you only have five slots. Fill them with boxes that can't do anything and the level is lost. The order you choose is the whole puzzle.