CS50x Puzzle Day

CS50x Puzzle Day, previously known as Facebook Puzzle Hunt before 2018, is a puzzle hunt hosted by the staff of the CS50 class (an introductory course in computer science) at Harvard, with help from Facebook. In some years, this event was additionally hosted at other university campuses, with the same puzzles. Puzzles are presented in a single packet, which is given at the start of the hunt. There is no metapuzzle. The event has run annually since 2014, with the exception of in 2021 when no hunt was held.