Enjoyed myself quite a bit, physics fun abound. Pacing felt great and the hat showed up just in time to add the spice of the bubble mechanic. Though it felt a bit weird that the fire mechanic never comes up again after the first area, at least that I recall. I also like the scale of the environment, really makes you FEEL like a small child, as well as make the tower more domineering.
Only negative I can think of is that at several points it felt like you could softlock yourself, especially when dragging crates and bubbling them up, if you fell back down while they stay on the higher level. Though I didn't try, maybe you already have a system to ensure that doesn't happen.
Excited to see what you add next time.