Here's a tip for game jam success: your earlier levels should be your tutorial, even if it's for non-basic stuff or combinations of mechanics. Here's my game from the first jam if you want to take a look at that. The first half of the levels were pretty much slowly introducing all the small things you need to know to be able to play this specific game well, all in controlled environments. Then when the game starts to mix them up it's not putting the player in any situation they don't understand and it flows more nicely.
(Also a skip level button in a jam is my other secret technique, if people really get stuck)