Very polished looking game, really nicely done! Feels great to control, plays nicely into the theme and has a great and fitting theme tune. The special effects also looked really nice along with the sound effects. Just very impressive overall!
One thing to improve maybe could be to not allow the player to just hold down fire (as I did) and turn circles constantly to keep killing enemies off-screen. And maybe add some weapon pickups to incentivize you to move around more.