Earlier quoted context omitted.
Same caveat applies to the "checkbox hack" or any other pure CSS solution. You cannot create accessible versions of most complex controls like tabs without JavaScript. (That first example could be created semantically and accessibly with / though!)
for "accessible", do you mean getting focused when pressing TAB key?
- Tabs should have an ARIA "tab" role [1], but doesn't accept roles [2].
- Focusing a tab must activate the corresponding tab panel [3], which requires JavaScript.
- Tabs should be navigable by arrow keys [4], which also requires JavaScript.
I want to be clear that I'm not trying to tear down your work. Your project looks cool and eliminating JavaScript is a noble goal. But unfortunately, as of today, it's still required to correctly build most complex controls on the web.
[1] https://developer.mozilla.org/en-US/docs/Web/Accessibility/A...
[2] https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/...