The goal is to drop blocks, called tetrominoes, down into a playing field to make lines. Tetriminoes are made of four connected squares each There are seven different types of tetrominoes. Levels have a set goal, or number of lines to clear. When the goal number reaches zero, the player moves to the next level. As the levels go up, the tetrominoes fall faster. A player receives bonus points if he can clear more than one line with a single tetromino. Clearing four lines is called a "tetris", three lines a "triple" and two lines a "double". Clearing two tetrises in a row is called a back-to-back tetris. The player can also turn a T-shaped tetromino into a hole, called a T-slot, to get more points. This move is called a "T-spin". A player loses when the tetrominoes make it to the top of the playing field. See "Issues" for information on the Level 29 Problem.