Love the hand-drawn style sprites in this game, fits the whole story-telling mood really well!
Also loving the effort that went into drawing the entire stage. It feels very seamless and natural, and doesn't have the "tiled" look that most platformers usually have.
Downside to that maybe, is that points of collision are not quite obvious to me, the particles are really good touch of indication, but I still found myself getting disoriented on what is considered solid vs background elements at times. Try to use contrasting colors or brightness to allow players to differentiate between solids or backdrop.
Some areas (the sewers), needs better indication of death drops. There are quite a few blind drops that I cannot really tell if there is a ground below until I drop down to find out. (Maybe either make the water higher so it is visible enough, or draw some stains on the wall so that I can tell that there is goop underneath or something.)
Beautiful work, thanks for making this!