A system for Tony Dowler's perfectly compressed micro-dungeon maps?
Try the ultra-concise Deeds & Doers.
Only players roll – 'to do' – when there is a significant risk.
The DM applies injuries and conditions with judgement, not hit points.
A game you can hold in your head.
Fantasy dungeons, sword and sorcery, all by suggestion. Pick your source; then where, who, why.