(mild spoiler alert) It took me 00:06:20 to complete and I enjoyed it a lot. I especially liked the ambiguous form state; I was never sure which part of the form is active or has been selected. I appreciate that it didn't feel needlessly unfair; e.g. when I accidentally clicked a "select all" button that undid all my work, there was also an "unselect all" button within reach.

Loosely related: "The worst volume control UI in the world", https://uxdesign.cc/the-worst-volume-control-ui-in-the-world... .