So, I played up until the boss, then just stopped playing after a couple minutes of fighting it. The framerate was jumping all over the place the whole time, and since I couldn't see my health bar (my screen 1920x1080, with space for the toolbar and browser tabs, so the game screen didn't fit) I never got a sense that I was taking damage. The enemies waves aren't very interesting either, and the boss has a lot of points where I'm not sure how one avoids being hit.
The visuals are nice, but I think the boss just took too long.