Concept: very unique idea, fits the theme well.
Gameplay: took a bit to adjust to, but once I did it was fun. The mechanics of the ghosts wasn't very well explained I feel, I wasn't sure what the potion effects did like what does it mean if the ghost gets black or bigger. The achivements, hard mode and bonus level are good editions, but I suggest focusing on polish first especially on such short timeframes.
Art: leaves some to be desired to be honest. The sprites are well drawn but rendered and arranged poorly. I highly suggest disabling anti-aliasing for pixel art (either in engine or when exporting the image, not sure which is the case here), and also using consistent pixel sizing. For the UI, text sizes are off at places and the layout is messy, overall it kinda gives an unpolished feel.
Audio: the music is alright, if a bit repetitive. The lack of sound effects bring it down a little.
Sorry if this comes off as a bit negative, I do recognize the effort. I think with a fresh coat of paint the came could be very good.