Move an icon to an empty square on the 9x9 grid. If you get five or more similar icons in adjacent positions (row, column or diagonal) they will disappear. If there are no icons to clear after a move, three new icons will drop onto the grid. The game ends if there are no more empty squares available on the grid.
Use this app on your phone when you stand in a long queue that seems not to move. You can try to reduce your frustration while you struggle to improve your high score.