Gaming AI learns Super Mario, could work on any NES game

Tom Murphy is a genius. He’s created an AI that can potentially beat any Nintendo Entertainment System (NES) title. Murphy, a CMU PhD student, describes his procedure (which he is calling “Playfun”) as such:

The basic idea is to deduce an objective function from a short recording of a player’s inputs to the game. The objective function is then used to guide search over possible inputs, using an emulator. This allows the player’s notion of progress to be generalized in order to produce novel gameplay.

As TechCrunch reports, it’s a “technique for automating NES games. The approach is amusingly elegant and surprisingly effective, requires no detailed knowledge of the game being played, and is capable of novel and impressive gameplay.” Here’s the video in action as the AI begins its first play through of Super Mario, level 1-1.

At first, the AI is twitchy at best. For the first try, Mario jumps up and down “forever” Murphy adds. During the next run, Mario jumps forward and gets stuck behind a pipe and for some odd reasons, he’s backwards. Playfun evolves and a few weeks later, the “future input” of the AI has predicted parts of the level 1-1. Murphy calls this “a series of sequences that are more or less coherent”.

Finally, Mario beats world 1-1. During level 1-2, Mario can even be seen practicing some interesting gameplay techniques, such as backwards jumping. After what Murphy calls a “breakthrough”, level 1-2 becomes even easier for the AI-controlled Mario. After some embarrassing deaths in level 1-3, Murphy switches to Karate Kid which uses the same AI protocols as Super Mario. It’s fascinating to watch the AI in action, knowing that it has not been tweaked in any way for a non-platform title. When Murphy does switch back to a platform game (Adventure Island), the AI kicks in and decimates the first level without much fuss.

“Games that move right and let you avoid obstacles” are best, says Murphy. Pac-Man fares well, and exploits bugs such as slipping in between the ghosts during a split second “safety” animation. Bubble Bobble takes the AI and extends the sequence far beyond the programming, “which is pretty impressive,” according to Murphy. Read all about Murphy’s plans to rule the gaming world here in his paper called “The First Level of Super Mario Bros. is Easy with Lexicographic Orderings and Time Travel . . . after that it gets a little tricky.” Skim through his work, it’s a fascinating read.

Steven Norris: grumpy curmudgeon


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