This is so good! I really like the idea of your task being not to destroy the hero, but to create a satisfying, balanced challenge for them. It's a little bit like playing the DM in a tabletop RPG.
All the bug enemies and the venus fly trap hero look great, and you've got a lot of nice crunchy effects when the battle is going on. I'm curious how you implemented your hero AI - we did a reverse shmup too (focusing on a bullet hell boss fight), and I only had time to make some basic repulsion, but your fly trap is smarter and takes the offensive while it avoids attacks.
Overall the presentation and polish and concept are great. Nicely done!