Great game, I really liked your idea for the theme and the ghost players worked very well. The puzzles were fun and I appreciated that each puzzle worked differently -- they weren't just a reconfiguration of the same puzzle concept repeatedly. I liked the NES-style graphics and the camera zoom work as well. I didn't have trouble on the third puzzle (the one where you need to move a platform up to the spikes to get a new ghost), for what it's worth -- sometimes when there are a lot of comments that a particular stage was problematic, it's good to hear that sometimes it wasn't.
My improvement comments seem to have been covered by other commenters, or by you: (ghost didn't respawn, but I used Esc. to fix; I thought the black screen at the end was a crash). Getting stuck on the sides of walls or platforms when pushing the arrow button into those walls/platforms was the biggest issue for me. The first large wall that you can move with a button, for example, was one where I 'stuck' to the wall. This sticking issue repeated on a few other structures. (Maybe using a Platform Effector Component, or making sure you have the layer designated properly on that object?). It also felt like I also couldn't jump to my full height at times, even when holding down the jump button -- not sure what caused this, but possibly related to the sticking issue as I was usually trying to jump onto something.
Overall, fun game, was happy to play to the end!