One By One is a puzzle game with one piece and one rule. A piece can only slide if it is in contact with another piece. Slide the pieces in the bottom board to match the pattern in the top board. You get points if you use fewer moves than what is shown.
In timed mode, you have ten seconds to make a correct match or you get a strike. Three strikes and game over. In untimed mode, you get a strike each time you take more than the shown number of moves to make a match.