I have made the game Tetris using a PIC16F84 running @ 12MHz. Tetris is an old Russian computer game where you should try to fit in block into a play-field, quite simple but really fun. All blocks are built from four bricks (the name Tetris is derived from the ancient greek word for four: “tetra”), there are seven combinations of the four bricks as seen here to the left. This version is using my PIC Game System as platform, generating a video signal in software. The only hardware used for the video generation is two resistors forming a 2-bit DA converter. Link.