This one is really cute! I like the floaty mechanic, makes for a unique take on a platformer.
I have to echo something another comment said, there are a lot of non-colliding background elements which look exactly like platforms which was a bit frustrating. Consistency in which assets are solid and which assets are not is really important for a satisfying player experience.
I did like it overall though, and it's very well-made for your first project!