hi, TG. i believe the Hosts will agree that we've seen plenty of games in past 20 Second Game Jams that do exactly what you're planning but might seek some clarity; Story progression, level Unlocks, more Bosses to battle, etc, are all fine (and welcome) so long as each is capped at 20 Seconds and nothing is carried over to the next beyond the plot and flavor you plan on adding to the pot :)