RfC: New Key foot_scale=* ("now for something a bit recreational")

Given foot_scale came up in the first thread (thanks @ezekielf) I’m going to keep it. :slight_smile:

I’ve splintered this off into a third thread and added in some language around slope angles into casual and attentive. hands_for_assistance already mentioned it, and scramble doesn’t really require it. I’m unsure of how to word it on surefooted, but feel like the accessibility expectation and general description give a solid vibe to work off of.

I’ve also tweaked wording a little bit here and there: