Movie based on the Cold War, in which a high school aged hacker looking for new computer games in a software company accidently finds (through a 'backdoor') and engages an advanced AI computer system at NORAD that plays "war games". While this is happening, NORAD puts their missile defense systems online with their computer system to take people 'out of the loop' of launching missiles after one of their men refused to turn his key when ordered during a routine drill exercise.
The hacker is eventually detected by gov't officials, is found and arrested. Oddly enough, the hacker is transported to NORAD, tries to explain the situation but all attempts fail. Then, the AI system eventually controls the US nuclear arsenal and starts stepping things up by accessing the missile launch sequence and starts to run through random codes to try to launch the missiles, which presents a possible real nuclear war situation.
The hacker eventually escapes, finds the AI system's creator, who was listed as dead but was living under an alias, and returns to NORAD. As the situation intensifies and they make many attempts to shut things down to prevent a war, they engage the computer in a game of Tic-Tac-Toe to try to teach it there's no way to win. Eventually, it switches over to running thermonuclear war scenarios, hundreds of them, over and over.
The computer, after having examined all the outcomes of destructive competition - Global Nuclear War Scenario - essentially reveals that "The only way to win is not to play."
For discussion of wargaming as a hobby, see WarGamer.