Right, the feet should bonk at the metal bar from below, and the feet should stay below at all times.
Over the years, I've grown wary of allowing any motion into solid terrain at all. Avoiding such motion will make for easy mental models and it also prevents bugs. There's still a lot of such moving into terrain in Lix. E.g., too many parts of the code move the lix first and then test for terrain, when instead we should test first, then move, then test again.
Would she bonk and fall down if the gap was a bit larger?
Yes.
She bonks when the gap is 4 pixels (2 lo-res) high. She ascends when it's 2 pixels (1 lo-res) high, even without any permanent skills. Looks like this ascending has been a result of the code for over 10 years and we never found it.
I wonder if Silken (the green player in the gif) has found this himself before the session, then wanted to trigger this behavior knowingly here.
-- Simon