Background objects look too similar to platforms. This has caused confusion a couple of times. Trying to dodge homing projectiles in tight quarters can lead to unavoidable damage, especially when you place multiple of those enemies within range of an area where the player will have to wait for a floating platform. Consider reducing their rate of fire, their shots come way too densely to weave through, and be more judicious about using them in any tight area where the player can't jump properly. Stage design is unclear and can punish exploration in a game that seems to require it - unclear if a drop leads to more stage or the damaging floor at the bottom in many places.