Awesome game! Hope to see more stuff (everyone's suggesting HUMANS THAT do activities that I would LOVE to see) also if you make humans make sure they put out fires (With a fire extinguisher, also make it possible to disable it so we can BURN THEIR HOUSES >:D) and also I favorite it as 2D Tower Defense from water :3 (look at my Water Defense Level if you wanna see what I am talking about!)
Powers are for temporary effects. You can already make things not collide via Spawn > Properties > Ghost.