here's a 60 degree incline. the player correctly goes from falling to slipping to grounded, although i'm really not proud of how poorly Unity's tools are set up to have a robust system for this stuff. i feel like i have to hack every little thing...

and additionally i realized before stopping tonight that i should separate "ground surfaces" from "slip surfaces" from everything else (like walls, ceilings, etc.) because at the moment there's only "ground" and "not ground, in which case you slip."