It’s a good one today folks. Modern Vintage Gamer had a look into how the CPU opponents of two of the most popular and foundational fighting games, Mortal Kombat 2 and Street Fighter 2, cheat against players trying to progress far into the game on their meager financial resources.
Their Mortal Kombat 2 video (11 minutes) is three years old now and has racked up 1.5 million views, but it’s well worth reviewing. While MK2’s source code is not known to the public, UK3 for the Playstation’s source is known, and is suspected to be similar to that of the earlier game, and uses a dynamic difficulty variable called diff. MVG uses this source to make an educated guess of how and when MK2 decides to cheat.
Lest you think it’s only us filthy Americans who would resort to such underhanded means to rob honest teenagers of their quarters, Street Fighter 2 does it too! Much more recent is MVG’s four month old video (9 minutes) on that game. (If you’d like to skip the video’s preamble, this link is queued up to the beginning of the cheat discussion.)
In brief, the games use input reading and the ability to perform complex moves lag-free to get an edge over human players. A player would have to enter moves on the joystick and with the buttons, while the CPU can just do them, without having to spend that time. And by reading the player’s inputs (like the Ironknuckles in Zelda II), they can react to player actions reliably, where a human opponent would have to judge based on vague visual indications, and then respond with a move to counter your action that was already in progress.
