But if you run and jump, the head does not move so high. I don't know if there is a 100% reliable way to detect jumping by tracing just head and arms. But the traps requiring ducking are on the list.
The jumping/going between platforms... I will have to think about it. I still have some other issues to solve, for example walking through walls. On a similar note there is walking over the edges. Falling down will be an uncomfortable experience. Having it in game, could add tension. Although people get nervous in higher places anyway.
I don't want to have completely abstract symbols that would be hard to remember. But having circles, triangles, combinations of them, reinforced by colour, should be easy to remember. I'd rather avoid letters (mostly because of the lore).