Tetrominoes, shapes composed of 4
blocks each, are falling down the screen, and
one has to direct them so they will fit to the
wall on the bottom. When a line of blocks has no
gaps, it is complete and disappears.
The maximum number of lines that can be
completed simultaneously is 4, since at least
one block is required per line. This can only be
achieved with the "I" tetromino: doing this is
known as a "tetris".
In order to master the game, the technique of
sliding a piece just before it sets is
invaluable, as well as using both rotation
buttons, when available.
