Try out The One Winged Angel. That just beat the hell out of me. I had a shark coming every 30 seconds and the screen was constantly full of screamers and rhinos. All in all, awesomely epic song about the hardest boss eva equates to an awesomely epic level that will destroy you. Way harder than Through the Fire and the Flames, which I also did.
The game seems alright, as everyone says. I agree with most of the comments here, from bullet size to spamming being obnoxious. Anyway, I'd say, at this point in production, it's just a 2/5. The fact that this is in such early stages stays my hand from putting an actual ranking yet. I'll favorite this and check for updates. I'm interested, to say the least.