The candidates were all utter dimwits. (Spoilers.)
It was hinted that these seven people passed several tests to get here. They're the brightest potential employees in the land! Only one can be the right hand man/woman to the CEO of the largest company in human history. (Remember. Compared against countries...their GDP would be 8th in the world. 6th by next year!) Yet...
-Not until 27 minutes into the film did ANYONE consider the possibility of using Candidate 2's paper as a "test subject." It's so hard to remember a total of three rules verbatim!
-Candidate #4. There are seven pieces of paper in the room, forgetting the one torn into pieces. She is handed 1 rolled up piece of paper to set off the fire alarm. Where the hell did she think it came from? There isn't much to keep track of in the room. So she lights her own paper on fire, happily watching it burn, without realizing that it has to be SOME candidate's piece. Hell, NO ONE questions what's burning. They're just a panicked, giddy little hivemind.
-Ignoring the fake candidate/CEO's comments. Come on. He's heavily implying that he can see something. He's quickly written off as a "nutter", but they believe he's a genuine candidate so he must have some modicum of intellect. Yet again...NO ONE tries on his glasses for fun. Until the final minutes when Blonde has her magical epiphany. The room is nearly devoid of objects. The fact that no one's sight line was drawn to the glasses and/or had their curious piqued is astounding.
-Revisit the guard after the lighter. Took them long enough to figure out they could screw with the guard. Logic dictates you immediately take his gun and holster, so no other jerk can use it on you. (This is the best job EVER. Stakes are high.) Hell, strip him bare. Wear his headset and try listening in on the other room. Get creative.
-White. Look at that watch on your wrist. You set it for a reason. You keep looking at it for a reason, despite the large timer in the room. (Fun fact: There's about 15 seconds left when the guard gives him "special treatment" and shows him the actual time, a thinly veiled moment purely for the audience, as everyone else was quickly escorted away. Secondly. The Blonde takes 83 or 84 minutes to dismantle the puzzle. How about no one wins?)
-Blonde. She wins. Lucky, as I would've disqualified her for leaving the room. It was a gambit to keep one foot in the room, as leaving the room wasn't strictly defined. To me, if half your body has passed the border of the door...you've initiated the process of leaving the room. So leave.
While the acting wasn't stellar (re: Dark was terrible), the lack of an intelligent script killed this film for me. Defenders of these characters will claim high pressure, extenuating circumstances. I say you don't get to the final 7 for a position of this magnitude without some superhuman fortitude. I presume the majority of my friends would've "won" in this simple scenario.
Now to be slightly less of a buzzkill, I'd probably give it about a 2.5/5. It kept my curiousty however much the characters frustrated me. I don't see a repeat viewing happening anytime soon though. I'd rather revisit Circle or even any three of the Cube films.