This is good drama, at list it picks you up and is intense, game is interesting, but there are plot holes. Yes, they are in every drama, but I think here quite important parts of story are unrealistic and unbelievable: reason Woo Jin was pulled in game (even if someone wanted him in game, there would be so many ways, but calculate so complicated way is just unreal), his hate and obsession to Kang Do Yeong rom the very beginning, with no reason he starts investigation.
FL is too unrealistic naive and stupid and for some reasons everyone want to help her, and really smart genius coldhearted guys are interested with her persona, why?
Also the drama has lack of deep relationships. yes, romance isn't necessary in dramas like this, but there must be some emotional relationships, story needs that part too, without interesting and emotional relationships, chemistry drama becomes dry. hate, love, strong friendship, trust/loyalty but with reasons, so we could trust and feel this relationships. random people playing together and every relationship is only for game, and the ones which aren't for game are so unbelievable and dry...

Best part of the drama is Shin Sung Rok,
his acting (as actors acting and characters acting) his crazy charisma, facial expressions, everything about this actor and character is perfect!

though why is he soo bad and villain is also not believable. because drama and protogonist needs villain? then make some realism, show me why is one smart guy, even liar and manipulator so bad, why is this game something evil? and his maker devil? this is just reality show, if people except to be part of it, they should except it's rules. show and it's maker saying "this is game of lies and manipulations" so what? is this criminal? if you (for example FL) are so good and angel, why you are playing it and then critic, also searching some conspiracy theories behind it...

ML and SML, Woo Jin and Kang Do Yeong and even Jamie (she did worst things than Doyeong) are basically same, they are very smart, coldminded, they manipulated and lied to other players (this is the game!), maybe in their souls they are different and Woo Jin is better poerson, but in game and in events what we see Kang Do Yeong didn't do anything worse, so why is only he evil and someone who should be lost and betrayed from everyone? drama doesn't gives believable reasons.
Somehow everyone, players and all other characters, everyone hate Kang Do Yeong, are against him and look at him like worst enemy. WHY? he isn't nice person but no one in this show (except stupid FL) is angel, so why is he only evil? why everyone fights him so aggressively? even at the end, when we know what hell he gone through noone compassions him but hates him more