Call it cynicism or grasping, but Hydrocity in Mania just feels so paint-by-numbers and "there", and I feel it might have been put in just so the team could avoid putting Ice Cap in it and embracing a fad.
It goes on for eleven years, has that annoying part where you're outside and have to go on those spinning electric things, I get lost very easily, and it has the most annoying act 2 boss in the game. Blegh.
The Act 2 boss is indeed problematic but I otherwise can't really agree about Flying Battery being a weak (remixed) stage at all. The magnetic properties of the electric shield and the outside/inside switching gimmick really expands on the original level to great effect.