A move consists of sliding either the top, bottom, left or right half of the tiles. When it is unmixed, each of the four quadrants contains only tiles of the same colour.
What makes this puzzle difficult is the fact that for each move half of the rows/columns slide together. The puzzle comes in 3 different sizes and 4 different colour combinations. We think the medium size puzzle with 4 colours compares in difficulty with Rubik's Cube. But if that is too hard for you, try the smaller size or one with fewer colours. We also have a premixed puzzle for each size, where the challenge is to unscramble the puzzle in the minimum number of moves.