Interesting idea for a mechanic, though I think the optimum strategy is just to make maximum amp and frequency to cover as much of the screen as possible.
Possibly you could avoid this by having hostile mobs that attacking damages you, or some other mechanic to mix up the behaviour, like a sawtooth wave etc.
I like the graphical effects like the various fades and animations, very polished and makes the game feel very responsive to play. Great work!