Cool game!
I liked all the shaders, but I had to disable the heat shader in settings because it was making the game lag. I enjoyed spamming the left mouse button shooting aliens. Tried holding it, but it seemed to shoot a lot slower (about 1–2 shots per second).
The fast movement in combination with being able to fall was frustrating, but I guess that's part of the challenge. The spinning earth on the title screen was interesting! I didn't get what the pickups did (except for armor; found that out after paying more attention to the health bar), but figured they did something good (perhaps more visual feedback would help?). The heat damaging the player slowly gave an intense feeling to the game.
Thanks for submitting the game!