I really like the scene transition, which appears like a mouth chomping down! The music in the title screen is nice, though it does call attention to the fact that there's no music during the levels.
As mentioned by others, I also had the problem that damage does not reset between attempts, so once the damage bar is full every reload immediately ends in failure.I got to level 5 before this happened, and up to that point the concept of changing only appeared once, when turning into a telephone. Which is a neat idea, except the only purpose of turning into a telephone appears to be that you must then turn back to the usual flower vase to progress to the exit.
Speaking of the exit, as has also been noted by others, there's a problem where the collider(s) do not match up with the visuals. It's entirely possible to do what appears to be a safe landing only to explode immediately. I'm not sure why the sides of the exit are as lethal as the moving obstacles and was very surprised when, at one point, I was able to land on the regular ground with only a bit of damage instead of instant death.
From what I've seen of the first five levels, they're all very similar in design. This could actually be advantageous giving the concept of controlling a shapeshifting object, if only that was leveraged earlier on. For example:
Begin the first level as a flower vase as is the case right now. That's fun and a bit weird and perhaps a little bit of a reference. Then, in the second level, start as a different object like the telephone. (This gives the player the feeling of "Oh, this is different!" instead of "Oh no, not again!") In the third level, start as a larger object (ideally not the same object from either of the first two levels) and shift to a smaller one when encountering a narrow gap. This way, rather than starting as the desired shape and being forced to switch back and forth, you can show off how shape changing is beneficial to the player rather than detrimental.
Structuring the levels this way can give a sense of progression through more complex gameplay, as well as increasing difficulty. Since the game is called Polymorph and the concept is shape changing, introduce that very early and show how it makes your game unique. :)