Update 1:

Thanks to primarily Kjell's help, the exe still falls within 64kb (the sound library inflates this many times but that was outside of the scope of this project)!
Update 2:
The framerate and code are better, sound is less irritating, some things are rebalanced a bit... It still doesn't do anything fantastic nor spectacular but maybe some fun can be squeezed out of it (once you get the fire rate up)? Here is the end message, after beating level 35:
"…Thanks to: ZGE Chat Channel brigade (Kjell, Shviller), ZGE forum (Rado1 for the Sunvox library). …and authors of ZGameEditor, SunVox and Fony."
Edit: Removed obsolete stuff.