Screenshot: Joseph Harris (YouTube)

Mike Tyson’s Punch-Out!! for the NES hasn’t had a new speedrunning world record in over a year. The last one recorded was set in April 2018 by Summoningsalt with a time of 15 minutes and 10.5 seconds. But over the weekend, Summoningsalt returned, shaving a fraction of a second off his previous record. He was able to do that thanks to a new strategy for manipulating the fight against King Hippo in order to expose his weakness as early as possible.

King Hippo is impervious to every attack except when he opens his mouth, at which point he grabs his shorts to keep them from falling down and leaves his himself defenseless. However, there’s generally no pattern for when he’ll do so. He might open his mouth early in the round or continue to throw jabs, an outcome that can sink even the most expeditious speedrun attempts. On top of that, he needs to do it at least three times for players to KO him. But thanks to new insight into the game’s internal workings, it’s now possible to greatly increase the likelihood of King Hippo opening his mouth on all three of his first punches.

In a Google document released on July 7, Punch-Out!! speedrunner Lucandor158 and his brother, Zoxsox, detailed their research into how the game’s internal memory affects when King Hippo will open his mouth. “RNG in MTPO is based off the memory address 0018 in RAM,” they wrote, referring to how the game mathematically decides which move an opponent will use. “This value changes every frame based on 2 other memory locations: 0019 and 001E.”

The value in 0019 is determined by players’ cumulative controller inputs during a playthrough, looping every time that value surpasses 255. 001E simply keeps count of the number of frames that have occurred. As a result, it’s possible to influence the values that appear in 0018, and thus whether King Hippo opens his mouth when the fight starts.

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“When hippo decides whether or not to open his mouth, he looks at the 3 rightmost bits of 0018. If these bits are 001, 011, or 110, he will open his mouth,” wrote the brothers. “Any other combination will result in no open.” While the math going on behind the scenes can get a bit complicated, the strategy itself is more straightforward in practice.

“First punch involves starting the fight in the correct 8-frame window, which isn’t too hard to do—I probably get this part correctly 90-95 percent of the time,” Summoningsalt told Kotaku in an email. “In order to get the third punch to always be an open, the frames you hit the first two punches on must add up to either 3 or 4.” He added that it’s still hard since there are no visual cues to help with counting frames, but after practicing, he’s been able to create the conditions for King Hippo to open his mouth a third time consecutively about 75 percent of the time.

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That’s what happened during his attempt over the weekend, with the King Hippo fight taking almost two seconds less time to complete than normal. When combined with some other short time losses earlier in the run, he was able to secure his new world record of 15 minutes and 10.11 seconds.

Lucandor158 and Zoxsox speculate that this is only the beginning of a new era in Punch-Out!! speedrunning. In the past, world records like Summoningsalt’s have leaned heavily on skill and experience, but the brothers believe the same RNG manipulation could potentially be applied to other fights. It’s even conceivable that the entire game could be reverse engineered in this way to reveal the perfect route through it, with every bob, weave, and punch planned out ahead of time. Not bad for a 35-year-old NES game.