Tap a piece, then tap an empty square. It travels there if a path is open. Line up 5 or more of the same piece in a row, column or diagonal to clear them. Miss, and 3 new pieces drop in where the small faded previews show. Move a piece onto a preview to send that drop somewhere random. Use your tokens wisely. You get 3 undos per game, plus 1 more for every line of 6 or more. Score high enough to earn up to 3 stars per level, and stars unlock new Worlds.