Nice work on this one ! Some areas were a bit technical to go through (might have died a few time on those spikes ^^). Fun little game overall, enjoyed playing it :)
One comment I could make is about the changing of shape, I think it would have been a good idea to constraint the player on the power it has to use based on the location. Often times I found myself in fly mode which was overpowered in some levels.
Also I found a small glitch with the sprites which stays in water form when switching quickly to fly mode.