Contextual Control Hints

Have some UI element in the corner that shows (important?) key bindings for the current context in an overlay at the corner of the screen, eg:

[x] In attachment mode: (F- Cancel, LMB - Select)
[x] With grapple limb attached - (LMB - Detach Grapple, W - Retract Rope, D - Extend Rope)
[ ] TODO - other limbs...
[ ] TODO - way to clear? disable? toggle?
[ ] Attached to some control console: (W - Move crane left, D - Move crane right)

stjahns / INTD450