I'm not entirely confident that a lot of people even knew of this one, but it's really great. I watched it in early 2016 with a friend of mine, and I can call this one my favourite 2016 movie.
Two girls who doesn't understand human values live inside a massive computer program with gateways to a pretty much infinite amount of human world simulations, complete with memories and experiences for every single human who lives inside the simulation. Some of these simulations contains viruses, and these girls destroy the corrupted simulations. Then a girl who understands humans showed up inside the program and the two girls take care of her.
Now, don't expect much from the world the writers have built, because it is kinda condensed. But it is really, really comfy. The soundtrack is nice, the art is great, and the limited cast made it really feel like something. The soundtrack especially, there are three insert songs that sounds absolutely wonderful. The art especially looks better than real world, so that's something. I'd attach a picture here but they're a bit too large, I suppose?
One of my favorite moments in the movie is the bit where the three girls, completely alienated from the concept of humans, even their culture, decided to visit the simulations again and experiences every single thing that's good in this world. And the bad ones, like war and disaster. The other is the ending, but I won't go to that, obviously.
I'd kill to experience this movie for the first time again.