I looked it up (on Google of course) and it seems like this is one of Google's recruitment channels.
You get access to a terminal and a text editor:

Here are the commands you can execute:

You have a week to complete each challenge. I've done 2 of them so far, and requested the third one - they have been very enjoyable and I've already learnt a lot from them.
I'm pretty sure I have literally zero chance of being hired by Google (and I'm not even sure I would want to work for them even if they made the mistake of wanting to hire me), but this has been super interesting so far. And yeah, also a huge time waster, I've been thinking about making the solution to the third challenge more elegant and performant all day instead of doing my actual job.
If you are interested in AI safety - whether you agree with the recent emphasis on it or not - I recommend watching at least a couple of videos by Robert Miles:
https://www.youtube.com/@RobertMilesAI
His videos are very enjoyable and interesting, and he presents a compelling argument for taking AI safety seriously.
Unfortunately, I haven't found such a high-quality source presenting arguments for the opposing view. If anyone knows of one, I encourage them to share it.