
Tetriminos are game pieces shaped like tetrominoes, geometric shapes composed of four square blocks each. A random sequence of Tetriminos fall down the playing field (a rectangular vertical shaft, called the “well” or “matrix”).
The objective of the game is to manipulate these Tetriminos, by moving each one sideways and/or rotating by quarterturns, so that they form a solid horizontal line without gaps. When such a line is formed, it disappears and any blocks above it fall down to fill the space.
When a certain number of lines are cleared, the game enters a new level. As the game progresses, each level causes the Tetriminos to fall faster, and the game ends when the stack of Tetriminos reaches the top of the playing field and no new Tetriminos are able to enter. Some games also end after a finite number of levels or lines.All of the Tetriminos can fill and clear both singles and doubles. I, J, and L are able to clear triples. Only the I Tetrimino has the capacity to clear four lines simultaneously, and this is referred to as a “tetris”. 