I just have updated it once again, now it's written in MonoGame and works pretty well. Furthermore, gameplay is much better, way more intuitive and I fixed everything you have mentioned. There is level select option now, so now you can play where you left off after gamw over and there are no more platforms where you can fall through. There is more so feel free to give it a try ;) (if you want to). New version is Alpha 2.0.