Relearning to code as a game designer

How good at programming does a game designer need to be? It depends, obviously, but despite doing just fine without doing any serious scripting for the last couple years, I can't stop asking myself that.

I mean, what if [cool studio I'd love to work at] asked to me to prototype something?Could I do it efficiently? And recently I've seen a lot of openings for technical design roles.

Just figuring out what I should do about that (if anything) has taken so much mental energy away from me. So here's what I ultimately decided...