progressive enhancement of open/close animation with calc-size()

[argyleink]

https://codepen.io/yisi/pen/MWdajwr

(coming soon)

[bramus]

Better to declare interpolate-size: allow-keywords on the details element. calc-size() is only recommended if you want to do calculations on the computed size. In most cases you don’t need to, and adding interpolate-size: allow-keywords is the simpler opt-in.

(If you want, you could set this on :root in your projects and be done, as the property inherits)