I've been fixing some collision stuff I didn't like.
The player collider has this shape in the demo:
This shape causes a few issues, collision with the environment isn't very realistic. The player can't stay still on staircases and it can climb over handrails and fall to its death.
I replaced the stretched sphere with a more specific shape:
This solves those issues. The margin of the collider was also changed to get rid of twitching.
I also increased the gravity, so things are much less "floaty" and the player doesn't fly up stairs. Invisible collisions surfaces are working now.
I've been committing these changes to the GitHub repository, take a look to see what's changed.