Mac began his journey on March 28, 2011. His aim was to reach what Minecraft developer Markus Persson calls the Far Lands, the area at the very edge of the infinite Minecraft world where the landscape distorts and fractures due to a glitch in the game's underlying mathematics. "Pretty early on, when implementing the 'infinite' worlds, I knew the game would start to bug out at long distances," Persson told The New Yorker. "But I did the math on how likely it was people would ever reach it, and I decided it was far away enough that the bugs didn't matter."
Upon hearing about the Far Lands, Mac saw it as an opportunity to distinguish his own Minecraft videos from others. He set out with a compass (which always points to the player's original spawn point) and began walking in the opposite direction of the spawn point.
Mac has walked more than 700 virtual kilometers in almost three years. It is estimated that it will take him another 22 years to cover the Minecraft world's remaining 12,000 kilometers. He's documenting all of it on YouTube while raising money for the Child's Play Charity. Season 4 of his Minecraft trek has already raised $168,500 at the time of writing.
Mac and Persson's full interview with The New Yorker can be read here.