Art is simple and effective, cute character design and animations, but the level design isn't very fun.
The jump in-air 'cheat' is too easy/obvious to discover accidentally and trivializes the gameplay, but playing without that is way too difficult, especially for such a short game. There isn't really a difficulty curve. The challenges could have been broken up into multiple shorter levels, and the collectible floppy discs could have used a bit more. That second level is far too long and difficult for a second level, and it's odd that it lacks the floppy discs. The third level would make more sense in its place, some re-ordering would help, but breaking up the levels and defining a more engaging difficulty curve would be best.
Overall, it's a great visual package, good theming for a Trijam game, and well-scoped. I hope to see you explore more about game design and refining the player experience with your future endeavors.
Cheers,