In the center of the screen is the chute. This is where the shapes will fall, piling up at the bottom as the game progresses. To the right of the chute is the score box. As the level becomes higher, the speed at which the shapes fall increases. This is the number of shapes that have fallen so far.
Bits are the smaller square shapes that make up the larger shape.
For example, the shape shown below is made up of 4 bits. This is the number of rows that you have cleared from the chute so far. 4 - Moves the shape one space left. Q - Quits the game in progress. P - Pauses the game until any key is pressed.