Here's another of those games I used to play on the ST: Zap is tiny, both in size (about 8k) and as a game. There's nothing too groundbreaking with this one, just kill all enemies wave after wave till there's no more :). The enemies move fast with erratic patterns that intensify as you make progress. No sound but the graphics aren't bad (plus, 50hz arcade quality FTW!). I actually managed to finish it without any cheats - see how far can you get!