I really liked this first season, it reminds me a lot of Death Note with how it feels like a game with the stakes being lives. Each episode created new developments and by the end of the season I was breathless. The characters were likable enough that I genuinely cared about their safety, which is crucial for a show like this. My biggest complaint would be that not a whole lot goes on in terms of animation. Not saying the animation's bad, it's quite good, but as it's mostly dialogue based there's not much happening on screen. A must watch if you like big brain strategies or being way too stressed out over the outcome of a fictional scenario.

EDIT: I stand by the fact that the first season is a masterpiece, but don't watch the second season. I have never seen a show be ruined so quickly firsthand, though I've heard legend of such things. Only watch season two to see how NOT to continue a show, and read the manga instead.