UP2037603: I found that the enemies' shooting made the player take care to evade their attacks and fight well rather than being able to hold the shoot button while ignoring the enemies. This added an interesting challenge to this game, although I do agree with some previous comments that a checkpoint system that prevents failure from restarting the entire game would be welcome and that, to discern how well the player is doing, a health bar would be useful.
The art and sound effects both worked well and I felt that they'd been designed to be consistent with each other.