This is a great concept. It particularly does a good job teaching the player what each thing is and how to use them without much additional explanation or tutorial. I also like that there are at least a few levels for each ability where it really gets to shine (caltrops vs charging enemies, bombs vs a circle of enemies around you, etc.)
My only feedback on the audio is that the caltrops sound got a little annoying by the end of the run, but otherwise the sounds seem really well designed for what they need to do. For gameplay, there were a few times enemies spawned pretty much right on top of me that felt unfair. Moving them a little away if the player is too close might help fix that. I did run into one bug: I wanted to take the movement speed thing, but I already had two healing things evenly spaced so there wasn't room. I decided to see if dropping it on top of one would delete the existing one, layer them, refund the other, etc. but instead it seems it just crashed the game.
Overall, I had a great time with it.