[myfonj]

Sure, you are right about infinite non-interactive CSS animations. And it's true there are simple checkbox:checked or whatever:active hacks for interactivity without JS. But for "click to (re)restart animation" there is no better cross-browser way I am aware of than toggling on some trigger attribute and toggling it off on animation end event, hence the JS.

[myfonj]

Ok, so here is variation that contains zero JS and (ab)uses the "invisible_anchor:focus + sibling_anchor_pointing_to_previous_anchor" trick [0]. I'd prefer the original version, though. This is more or less a hack.

[0] https://myfonj.github.io/sandbox.html#%3C!doctype%20html%3E%...