Let's count the similarities to 'Saw'
Don't get me wrong, as a movie this is much better than 'Saw' (acting, direction, etc.) but it clearly was heavily influenced by it.
1) Trapped in a single room, playing a game to save their lives
2) Strangers (seemingly at first then it is revealed that they are actually connected)
3) At first, one guy thinks he is directly connected to the organizer and has insider information ('He wants to kill me because I put his daughter in a coma.... )
4) A mirror, broken in frustration, reveals more about the room
5) as it turns out, original suspect is also just a part of the game
6) The 'killer' was in the room the entire time
Anything else?