Super fun idea, very clean visuals and the concept is easy to grasp with minimal text to explain everything, great job!
The controls are a bit tricky to learn, but I think that's because our dumb gamer brains are used to use arrow keys and WASD interchangeably, so I was making a lot of mistakes that way :)
I think that the concept of stretching up and then immediately shrinking down to create some sort of "jumping" motion is very interesting and I was wondering whether it's possible to use that instead of dedicated "jump" button, but maybe it would be too finicky and annoying to use.
The levels were fine, although I didn't really click with levels with spikes. There's nothing wrong with them, but personally I think that the collision box could be a bit more forgiving, since walking into spikes (when those should be jumped over) never felt right and multiple times I found myself moving just a pixel or two to the left and colliding with one (although the reason for that may be that I just suck at platformers :D).