A great little puzzle game, it took me a couple hours to complete it, but as with any puzzle game YMMV on the time. ;)
The interface of the phone you find is pretty immersive - it does not feel like the simulation of a phone in a videogame.
The pacing of the narrative is stellar - you are given just enough info to know something is 'off' but not enough to be able to guess what is off until you continue snooping through this stranger's phone. And when looking back, everything makes sense with no glaring plotholes.
The puzzles are not glaringly easy but also not so hard that you'll want to rip your hair out in frustration.
My biggest praise about this game is its ability to also double as an entry level educational tool for the subject it tackles. It does a tremendous job at explaining things in a decent amount of detail while also being simple enough for people who know nothing about the topic at hand to be educated without too much confusion.
At last, I also deeply appreciate the amount of languages this game is translated to - for one, because it is a fairly text heavy game and secondly, because as said above, this nifty little game who doubles as a 'let's learn about a fairly obscure topic today' will reach a lot more people thanks to being in so many languages. As someone in a non-english country who knows a lot of people that are held back from enjoying games because of the lack of translations to my native language, thank you. :)