WarGames (1983)

WarGames is great fun. A teenage hacker breaks into what he thinks is a games company, and ends up playing "Global Thermonuclear War" with a military supercomputer that doesn't realise it's only a game. The hacking is simplified, but it's closer to reality than most films manage. And the ending, where the computer learns that some games simply can't be won, is a lovely idea. Should we hand life-or-death decisions over to computers? That question was worth asking in 1983, and it's a much more urgent one now.