Cool take on the theme.
I like the character sprite and the animations are really well detailed for each evolution.
Also like the fact that the evolutions themselves are dedicated for specific tasks, swimming to cross a large pool of water, flying to reach high up places, attack to clear enemies an what not.
I feel there are some small issues though, gameplay regarding movement and physics is fine and responsive, but i felt i could get stuck when activating levers so i'm not sure if i got stuck or if i was just locked into an animation untill the door opened, but the temporary loss of control was a bit disorienting. Then the background seemed to glitch a bit from time to time, i really like what you did with the distant platforms and parallax effects but sometimes they would randomly pop in or out of existence.
But other than these, the game is fine, and i like how the evolution aspect seems kinda inspired by demon's crest with the whole one transform = one purpose approach.
Solid base regardles i'd say, so good job :)