Thanks for your feedback! I made some changes and did a new upload. The link is in the top post.
I think perhaps there is a more exciting enemy death effect than that "grow really big" thing you could use.
Hm, I suppose I could go for "fall to the bottom of the screen" or "explode in a shower of pixels" instead, would that be an improvement?
I saw an enemy get stuck in a wall (one of the teal ones, if that helps).
I think they also get out again if you wait a few seconds. Was it one of the triangles (a "wonk")?
Also, I think that you should make the bluish stars shoot out their little minions perpendicularly to where the player shot them...
Done.
The controls felt awkward but I got used to them over time - I tried mouse only, but found it a bit useless since you can't retreat; keyboard only and keyboard+mouse were both OK.
Hm, good point. I changed the mouse to have left button move forward, right button move backward, and middle button (or mousewheel) to trigger the powerups. In case anyone still uses two-button mice, they can use space bar for powerups as well.
It took me a while to understand the powerups.
I've added some help text. Basically, every powerup except for the first (warp) has two permanent levels followed by one instant effect that can be used over and over again.