I like how the enemies swap with you as well. It makes it so you can plan for the next shift accordingly. The biggest problem to me was that the background is one solid color. This makes it hard to gauge how fast you are going and where you are especially when there aren't a lot of bullets on screen. This also caused the forced movement shapes to be pretty disorienting. Besides that the next biggest problem would be the lack of audio feedback for when you get hit. It can be hard to check your health while playing at the same time.