For starters, computers simply lacked the processing power to make things happen. Floppy disk-drive machines paled in sophistication compared with modern smartphones, and computer chips wouldn't hold a million components until 1989. Yet another obstacle dogged any dreams of AI from taking form. In 1984, the American Association of Artificial Intelligence held a fateful meeting where field pioneer Marvin Minsky, of all people, warned the business community that investor enthusiasm for artificial intelligence would eventually lead to disappointment. Sure enough, AI investment began to collapse.

Artificial intelligence has come a long way in the 20 years since International Business Machines Corp.'s Deep Blue beat world champion Garry Kasparov in a six-game chess match, or even the six years since Watson trounced Ken Jennings on Jeopardy! Computers have beaten top human players at checkers, backgammon, poker, and go. Add to the list Super Smash Bros. Melee, a 2001 Nintendo Co. fighting game that lets you pit, say, Mario against Pikachu. Humanity has MIT researchers to thank for this defeat, chronicled in a paper they published in February, but Melee isn't the only video game getting a lot of playtime from learning machines. AI software has cracked Super Mario Bros.; early Atari SA games such as Space Invaders; arcade mainstays Pac-Man and Mortal Kombat; even mobile favorite Angry Birds.