A group of Diablo speedrunners have proven conclusively that the three-minute "any%" world record that has stood since 2009 is a fake. This proof process required reverse engineering analysis of Diablo's map generation system, which has 2.2 billion possible legal outputs.
This problematic speedrunning video was uploaded to the SpeedDemos Archive by "groobo" Maciej Maselewski in March 2009. In the video, a magician has incredible "good luck" in the speedrunning process, and the final time is 3 minutes and 12 seconds. This speedrun falls into the segmented "Any %" category, which means groobo can use certain allowed tricks, save the game and re-run parts of the session to get a better time, adding the best scores from each section to get the final time. The "Diablo" map generation research team said that groobo's manipulation of the game went far beyond what was disclosed or allowed.
"It seems extremely unusual that the floors above and below are right next to each other so many times," speedrunning expert and TASbot maintainer Alan "dwangoAC" Cecil said of groobo's seemingly unlucky run. "We wanted to find some way to recreate that."
Speed pass video:
The "Diablo" map generation tool was mainly developed on Github by Matthew Petrov, and its development required reverse engineering of "Diablo". It quickly displays the entire dungeon layout beneath Tristram, including item, exit, and quest distribution, with game-specific "seed" data. These seed data correspond to the layout randomly generated in a game process of "Diablo". The seed data of a game process will be set at the beginning of the game. There are 2.2 billion possible legal variations, each corresponding to a single second on the system clock between January 1, 1970, and December 31, 2038. If the modders hadn't figured this out, this might have been a minor Y2K problem for Diablo.
Although groobo claims that he won this speedrun through sheer luck and skill, map generation tools prove that some of the extremely favorable conditions he encountered in the game can only occur on maps outside of Diablo's legal date range - you can modify the game to make it work outside of the legal seed data range, but it is unclear how groobo completed his particular speedrun in 2009. groobo defended his speedrun, saying: "This is a spliced speedrun. It has always been that way, it has never been disguised as anything else, and it is not part of any competition or leaderboard. This is clearly stated on the 'Speedrun Demo Archives' page."
But that doesn't explain the near-impossibility of the dungeon layouts he encountered, and other anomalies later discovered in groobo's speedruns, like the ease and speed with which he defeated Big Pineapple, or some mismatched details that suggested he spliced together clips from different versions of the game. There is a comprehensive analysis on TASbot to debunk groobo’s speedrun. groobo's 3:12 speedrun record has been removed from the Speedrun Demo Archives, but the video remains on YouTube for posterity. In the meantime, it's still listed as "Fastest time to complete a role-playing video game" in the Guinness Book of World Records, which has yet to respond to the Diablo map generation research team or ArsTechnica.
"It did cause harm," dwangoAC pointed out. "Groobo was accused of cheating in 2009, which completely killed people's interest in this speedrunning category. No one tried, and no one could do it." In fact, groobo's speedrunning may have drained everyone's enthusiasm for the project before speedrunning really started to gain popularity with the rise of live streaming, hindering the development of the "Arbitrary %"-centered "Diablo" speedrunning circle at a critical juncture. The good news is that Diablo's map generation tool is spawning a new "seed-only" speedrunning category, where players can purposefully choose a favorable layout from 2.2 billion legal seeds.