I unfortunately had one minor technical and one major gameplay issue while installing/playing:
For the Mac build, I initially couldn't run it, getting an error saying it was damaged and can't be opened. This isn't the usual "you can't open because it's unverified blah blah" message that I circumvent by right-click-opening, but I found a terminal command online to fix: "sudo xattr -rd com.apple.quarantine /path/to/Program.app". I wonder if this is even possible to fix on your end or if it's the default behavior for Godot builds on my current OS version.
And, unfortunately, the gameplay would freeze (with asteroids still bobbing up and down) whenever the enemy got around half health. I played three times with the same result :(
That being said, I deeply wanted to play this game to completion, as I was hooked right away by the presentation and mechanics. The instructions on the game page were definitely required reading, so if you were to double down on this game outside the jam's 64x64 restriction, UI would be a focal point (as you already know).
Also love those stars in the background that flare up horizontally and vertically! Very nice detail.