i remember it being pretty good in the beginning and not bad towards the end. it isn't making any top 10 lists but it was enjoyable with a unique premise
I thought the story was horribad and the main two characters were not likeable at all. Also, since I watched this anime for the first time only 2-3 years ago, the concept of terrorists disseminating their messages via viral riddles on a Youtube-analog already seemed quaint and outdated to me.
It had very good art direction and animation, though.