My only real complaint here is that the door that required frequency B looked the same as the ones that took A. There was a moment of confusion when I tried to unlock it and it didn't work.
Overall this was fun and I'd definitely play it again with a few levels added.
The upgrade sound effect got to be a bit much though. I feel like it lasted to long and was a bit too loud.
The controls might have felt a touch too slippery, nothing you can't get used to.
Like I said, if you ever expand this and add more content, I'd be interested in playing it.