The movement and shooting feel really good, and a lot of the small touches make the game great. The intro, text effects, and the intensity select screen were engaging.
At one point, it was pretty hard to see the enemies against the dark background. I could also see it being part of the game design to make it hard for the player to see where they're coming from. Maybe consider increasing the visibility of that dark background section.
Great work and I'm looking forward to what you put out in the next phase!