If we're talking about what is in the spirit of the jam, we prefer one amazing, re-playable 20 second level, but you are allowed to have multiple levels. We also prefer that the levels are not progressions of previous levels (i.e. if you played them in a random order, everything would still work).
Random levels, random enemies, traps, etc is fine. We discourage progression between games/levels because it stops being a 20 second game and becomes something much longer. But this is not something that would get a game disqualified, as long as the first 20 second experience conforms to the rules.
