This was excellent! The transformation mechanic and how it evolved in different ways and with relation to the turning of the tower was fantastic!
One quirk I noticed is that transforming back into the mage after jumping with the frog still allows access to the double jump, which allowed me to sequence break getting some keys (or, at least, I think that's what happened. There was a portion of stage 4 I didn't even interact with since I was able to get the key early with that extra jump method, so I assume it was unintentional). Even if it is unintended, however, I still enjoyed pulling the trick off, so I would consider it to actually be a feature!
The music and artwork were both great as well! I really enjoyed it!