Probably everyone knows how play Tetris game, as the rules of the Tetris are known to everyone. Tetris game is a puzzle with the shapes each consisting of several squares, that are falling down the well. When playing a Tetris game, one turns them or moves left and right, trying to arrange the shapes in a line. When a line of squares makes a line from edge to edge, it disappears and all the pieces move down by a square. When the well is filled up, the player loses.
Seems like it's quite easy to play Tetris game, but as levels progress, you feel that playing Tetris game may be a real challenge.