Cool as a one-off use on some random blog contact form. Infuriatingly annoying if used somewhere you have to solve it with any frequency.

Cool, sure, good, probably not. I've never played Halo so I didn't entirely know what I was doing (do I shoot the blue guys too? it's not letting me through so I guess I do), and I don't doubt people couldn't even get what it meant by shoot. And god forbid anyone with disabilities that affects their mouse accuracy, or needs a screen reader tries to use it

Haven't looked at the devconsole but it'd probably be easily bypassed by someone dedicated.

Agree on the first part, but for the second... I think it depends on what your threat model is.

If you want to stop a dedicated attacker ready to spend time to attack your site, it won't work, but nothing will. If you want to stop a generic bot going over the internet and submitting all forms it finds with spam, this will work, and might even work better than wide-spread solution for which the bot has a countermeasure.

It has the advantage of being novel for the user rather than doing the same Google/Cloudflare/... CAPTCHA for the 10th time that day.