The gameplay is extremely simple, yet there's a real depth hidden behind its primitive surface. On a very small playing grid, you need to place right-angled tiles that are comprised of multiple colors. Lay them out in such a way that three or more identical colors touch, and you can clear that match from the board, and add a point to your tally.
On paper it couldn't be simpler, but if you want to get a really high score you're going to have to plan ahead very carefully indeed. Run out of space, and you'll be sent back to the menu screen, and so you always have to consider whether to keep building a combo, or free up some essential space on the board.