The sidebar of checkboxland[1] has a checkbox made out of checkboxes.

[1]: https://www.bryanbraun.com/checkboxland/

That's the second obvious omission from the article, other than the Conway's which is in the playground link.

Checkbox made out of checkboxes should then be put into an animation loop, zooming out to single chexel.

Also, morse code using checkboxes.