verall, this was an enjoyable ride but only after I started questioning what was going on. We'll come to that later...
Let's start with the positives: the cinematography, locations, and CGI are all beautiful. The first half of the drama is shot in Alhambra in Spain which looks stunning. Park Shin-Hye's Spanish is also fluent and really helps the integration of her family into their Spanish home.

The CGI is also really well done and well-integrated into the surroundings and with the characters.
You can check out the synopsis elsewhere but there are issues over how the AR tech works (SPOILER ALERT) - like how do they physically feel the effects of the AR weapons; how do they feel pain, how is powered - you know, the logical things.

But... ignore that and it becomes an enjoyable rollercoaster of a who-done-it adventure, and you end up forgiving it a lot of things. The acting is good - if you've only seen Hyun Bin in CLOY then it's weird seeing him be such a jerk at the start but his character develops due to the wonderful Park Shin-Hye and her family. The supporting cast is good too - with the evil Professor Cha (you'll remember him from Mr Sunshine - has he ever played a nice character?) and Hee Ju's little sister who is a great actress. EXO stans will love seeing ChanYeol as Se-Ju as the mysterious creator of the game.

All in all, I like it in spite of the plot holes. Give it a go.