I like the background music, the levers ended up just opening the door for me on most puzzles, so I never really had to deal with the conveyor belt platforms in any way, I'm not sure whether or not that was intentional though.
The spring pad really bothered me, it feels like it's applying a constant force to the player object, rather than working like a spring pad would. Switching out the sound effect and making this a "levitation field" or something would make this feel much better.
Picking up the crate also made it hard to see what I was doing and blocked most of the screen.