C64 Tennis

C64 Tennis is an unofficial fan port of Tennis, Nintendo's 1989 Game Boy game. It's not a remake: the original Game Boy game code was translated instruction by instruction into 6502 assembly. Ball physics, player movement, the CPU opponent and the scoring rules all behave like the original. An automated test compared the C64 version with the real Game Boy game, step by step, over thousands of game updates: they matched exactly.