The computerphile video describes a technique that can bokeh-blur a flat plane (like, something uniformly far from camera) so if you want actual depth of field you need to split your scene up into layers, blur them separately, and composite - but whatever tiny glade does appears to be more clever
The way stuff is generated and connected is super interesting too. I still remember the first tweet about this game twitter.com/anastasiaopa...
Also, it's written in rust!