Quern: Undying Thoughts is a first-person puzzle adventure game. It sets the player on an island to solve its mysteries. He receives guidance from two different sources, and soon finds out that these two guides have contrasting intentions. It is up to the player to decide which one of them they want to follow, sooner or later, they must make a permanent choice. Quern introduces reusable puzzle mechanics to the classic genre, forcing the player to think about the game as a whole, and not just as a series of individual challenges.