It's a shame about the malware warning, because this game is actually pretty cool. (Plus, it runs perfectly well in Wine.) The movement and the shooting felt really good.
The graphics were quite impressive. I think I actually wouldn't have been able to tell that you were forced to use a reduced palette. It all feels very natural, and the pixel art is very sharp.
I did find myself wishing that the camera was zoomed out a little more. I got sniped from offscreen quite a bit, and as Conquintor wrote, I ended up staring at the mini-map a lot of time.
Fun game, though! It's challenging but not unfair, and that's just the right balance to strike with a wave shooter like this.