Bricks'n Blocks

This is a solo game. A random sequence of Tetrominos fall down the playing field (a rectangular vertical shaft, called the "well" or "matrix"). The objective of the game is to manipulate these Tetrominos, by moving each one sideways and/or rotating by quarter-turns, so that they form a solid horizontal line with no gaps. When such a line is formed, it disappears and any blocks above it fall down to fill the space.