I know I suggested this caching here and below, and it isn't bad, but tell me if this would be better: what if we cached several (even 10s-100s) `div`s and then just swap their visibility?  Is that faster than setting the text here, which still shows up reasonably high on the profile at 0.4%.  I'd like to see this under 0.1%.

I suggest this because the frame time ping-pongs, which hurts exploiting frame-to-frame coherence like we do here.