Really fun and addicting game. I like the overheat mechanic a lot, it's simple but it's really satisfying to hit the middle each time. The sound cue makes it a lot easier to time it correctly, so I appreciate you putting that in. I also like the camera shake you get from hitting an enemy, it makes blowing them up a lot more satisfying.
I don't mind the amount of monsters, but sometimes a monster will spawn on top of me and I have to react extremely quickly to avoid it or else I die. You should also give the purple monsters and the enemy bomb projectiles a different color, because they blend in too much with the background. Jumping felt kind of awkward, it was a lot easier to just stay on the ground and under the platforms. Whenever I jumped I usually died pretty quickly after. I also think you should be able to shoot through the platforms, because the flying enemies are really hard to hit otherwise.
Overall, great game and I had a ton of fun with it. I played like ten rounds and managed to get a run without dying and a score of 52,300.