Really good art! And I liked the idea and your puzzles were very well designed! I played through to the end and always felt very smart when I figured it out!
My only problems were, the difficulty curve is really weird. The third level took me forever to figure out, and there were like a million conveyer belts I just didn't know what was going on. I think the levels should just be rearranged.
The movement is really slow and janky, I wish it was snappier.
The conveyer belts have two different sprites going on for the two levels they appear and that just seems odd.
The last puzzle was my favorite, I got a great "aha" moment when I figured it out.
Good job!