When Jonathan Schaeffer’s team at the University of Alberta announced in 2007 that checkers was solved, the result rested on a computation that had run almost continuously since 1989. Over those 18 years, dozens of computers worked through the game’s roughly 500 billion billion possible positions (about 5 x 10^20) to prove that perfect play by both sides leads to a draw, as documented on the project’s Chinook page.