With respect to the existentialsm inherent to some of the characteres, this could be a more personal opinion, but the thoughts discussed in the show are really interesting and I felt identified with a lot of them: freedom, human nature, life and death, etc. big topics that are not shallowy discussed as the characteres seem really coherent: characteres with a complicated past, with complicated personalities, with complicated thoughts about life, with contradictions and overwhelming emotions... you know, like humans tend to be.
I enjoyed the story a lot: I saw the whole show in one night (is very short so...) which means that it kept my interest and I wanted to know more about the story of the characteres and the resolution of the plot. This is pull out with only a few characters, which I think is very valuable (in some mystery anime they tend to include docens of characteres in the plot to confuse you and over complicate the argument).
To me the whole business with the computer and the maths its mostly complementary, it's not the centre of discussion neither the base of the argument (I work with coding and stuff like that, there was nothing deep related to it), it was just a way to show the sadness and freedom desire of the characters, as to them the digital world is a "perfect" world, as the digital world lacks everything that makes the real world a world where you want to escape from, a world where you suffer because you are constrained.
In summary, I highly recommend this anime to people that enjoys mystery plots and that also enjoys to contemplate exitentialist arguments that will keep you thinking for a few days later about these topics: some times I feel like I need another way to think about things, and the view this show presents is a very interesting one. Intersting thoughts, that's the best about this anime.
