I figured out how to make platformer engines properly. Finally. I'm genuinely so happy I made a platformer engine that didn't suck, actually. If you want to use this, please credit me, and if you want to adjust the hitboxes, make sure to adjust the other sprites (the sensors) too to make it work. I may expand this to a Mario engine soon, but that may take a while, and I can't guarantee I actually will. There's maybe one or two minor bugs, but they're easily fixable if you care enough. I know the collisions are a little silly but they work well so who cares.
All me. No tutorials were used!