This is a clever drama with an exciting plotline and complex characters.

Story: The story is well developed, and though I found it a bit slow in the beginning it picks up quite quickly. It keeps you wondering what these characters all have in common and how it all fits together. The games are well thought out and the twists and turns of this drama are very clever.  This helps keeping the suspense up as the drama goes on. The villain is complex and intriguing and the male protagonist is very interesting and clever. The conflict between the male leads is by far the best thing about this drama. The female lead didn't really appeal to me. She was naive to the point of stupidity and even though it gets better as the time goes on, she's still a bit dumb for my taste. She is definitely a damsel in distress. In summary  the plot is well written  and exciting. This drama does have an open ending though so if you really don't like those, you might want to skip this one.

Acting: The acting in this drama is quite good. Shin Sung Rok and Lee Sang Yoon both did and outstanding job as the two male leads. Shin Sung Rok really do nail those villain roles. I was not as happy with Kim So Euns' preformance. Her acting felt a bit too over-the-top for my taste, but this might be due to bad directing or the fact that she didn't have all that much to work with. I have not seen any of her other performances so its hard for me to judge. The other actors did a very good job as well. Not much lacking in that department.  

Music: The music works quite well with the mood of the drama. It adds to the suspense and generally does what its supposed to.  Well done.

In summary, this is a very well done drama with complex and interesting characters and quite a unique concept. If you like dramas with clever characters and suspense you will probably like this. And if you like dramas where the female lead is a damsel in distress, even better. And if you don't, just try to pretend she's not there. That's what I did.