I really liked the pixel art and the gun sound effect worked very well! The concept was outstanding and worked very well and having the ability for previous ghosts to shoot your present self added a lot of depth to the gameplay, and the addition of the boxes also helped to make some really good puzzles!
There were some minor things that could be changed however (not bad things just little quality of life improvements) like changing where the restart button is and masking the gam fullscreen. The spikes could have also done with standing out more maybe.
Other than these extremely minor complaints the game had some incredible puzzle design and seemed very polished mechanic-wise, overall I really enjoyed playing!