This game has potential, but one thing that definitely needs to be changed is dropping down through thin platforms: it should be immediate, because as-is, the final shaft has fake paths that get you killed before the drop-down finally registers. It's bad design to make it look like the player can go a certain way without actually making that route possible, especially when the player only has a split second to make a decision before being instakilled by vines.
It's also unintuitive that jumping on enemies will hurt them, especially since there are a couple you CAN'T jump on and have to shoot, which makes the ammo limit more frustrating than anything. I also recommend removing the forward-momentum.