The good news: it turns out I have an older copy of that C#/XNA platform game. Possibly the very same version in the screenshot.
That’s this one, for the record:
It’s so old, it’s made in VS 2008 and has a particle effect renderer that I scrapped after it wouldn’t upgrade to 2010.
And after testing it for a bit, I couldn’t find any in-your-face game breaking problems with the collision detection. It could stand to be perhaps a bit slower to better match the scale of things and fix the part where you can “hover” on the ceiling and…
Ah, right. That part. The part where you can’t actually go further to the left without jumping, and if you stand on the left half, face right, and then jump straight up you skip to the right.
I remember now.