The concept is pretty fun.
Art is a bit too simple, but the effects made it much better. The purple attacks are hard to notice.
For the gameplay part, I think you should make the platform shake just a little bit sometimes, or mabye add some recoil to the shooting, because I found the perfect stability spot and could stay here, and that would avoid that situation. Also add or increase the fire rate limit. You can literally hold the mouse button and you fire so fast that you can just spam without aiming.
For the theme, I haven't got enough retro vibes. Mabye for the gameplay.
For some reason, the game crashed at 4 minutes 18. And there was scaling issues : the tutorial only appear on 1/4 of the screen, and while the gameplay appears on the whole screen, the red flash appears on 1/4 of the screen too.
The limitation added even more challenge to the game. And the hitboxes were at player's advantage, which was very satisfying.
Good work.