Yeah, it was really hard... I was only able to do it by shooting without moving, which made the other weaker enemies come to me and then just shot them as they approached. Moving forward was instant death every time.
Funnily enough, this requires exactly the kind of pattern recognition skills that AIs are extremely good at. If I, as a musical layman, were challenged by this I would give AI a shot to solve it.
They have been doing some weird new captcha things I've been dealing with lately. One shows a 3D rendering of an object and then has you pick out that object as viewed from other angles out of a group of different objects and the other one I saw for the first time yesterday- it showed me a picture of a frying pan and told me to click on pictures out of a group of random things that were associated with the frying pan. It wanted me to click on pictures of burgers, so obviously it needs work.