The amount of juice is unreal and you were not lying about the railgun - it's just so cool!
The amount of particles and screenshake could be taken down just a peg as the readability of the level was not very good or maybe that's just me.
It seems like the supernova doesn't trigger for further levels either, at least it didn't trigger in 4 for me and 5 unfortunately bugged out and enemies stopped spawning.