My daughter and I played this game on stream: https://www.twitch.tv/videos/1928231849?t=00h02m20s
Overall, we had tons of fun. It took us a bit of time to realize that we could shoot, and how to shoot, and that made a world of difference. Thanks for telling us to use the ammo in the game!
We went for a sloooooooow creeping approach so we didn't need fuel, and that strategy worked very well. At the end we had so much extra boxes of health and fuel that we increased our max health and ammo a ton for the last stage, without realizing it was the end :)
In terms of improvements, I'd suggest adding an end boss of some kind, maybe with a room containing the rainbow power-up to max health/fuel/ammo first. Having some tutorial in the beginning to teach the basics of the game would be great too. I didn't realize we could shoot at first, and when I started shooting, I didn't realize we could aim!
When pressing the right trigger, I would fire multiple blasts when I really only wanted to fire once, so maybe having a single shot per button press would be good. There were also a few times a second shot would bounce (??) off walls and enemies without doing damage.
Overall, great fun for a prototype and I'm excited to see where this game goes in the future!