This game was really fun! I like how the cerebral nature of the game, where you're carefully planning which enemies to hit with which obstacles - how to spend your health as a resource is in stark contrast with the aesthetic - which is a duck riding a rocket and blowing itself up a lot. Really fun and charming dynamic there, which I love. I think the game shines in the longer levels, rather than the one-screen ones - but the one-screen levels do a good job teaching the player the mechanics, so I commend you on that!
The random movement of the slime enemies felt very out of place to me. Seemed to go against the core design of the game in a way that was somewhat frustrating to deal with. I wanted those slimes on a set path that I could take advantage of with my planning, but I just didn't get to do that, haha!
But, in summary, really fun game. Loved playing it!