[mkl]

One time in high school I made a Tetris clone (in one lunch hour!) with single pixels as the squares, and used the VGA video memory itself as the data structure for the current board state. It was in 320x200 resolution, so the pixels were pretty big (the game area itself was only a small rectangle of them). My version didn't detect when the pieces reached the top or keep score or anything, just the basic playable mechanics.