[reaperducer]

almost instantly

Or you can do it in CSS actually instantly.

And no, complexity generally doesn't negate this. Earlier this year I built a series of complicated medical forms for a healthcare web site that are all HTML + CSS + < 2K of jsvascript, and they all respond instantly because I did't lean on JS to do everything.

The pages are fast, responsive, work on any device, almost any bandwidth (think oncologists in the basement of a hospital with an iPad on a bad cellular connection), and the clients are thrilled.