At the edge of our solar system, a dark planet may lurk. In 2015, astronomers estimated a large distant planet could explain the unique orbits of dwarf planets and other objects. Since then, astronomers have been scanning the sky, hoping to find this planet.

In The Search for Planet X, players take on the role of astronomers who use observations and logical deductions to search for this hypothetical planet. Each game, the companion app randomly selects an arrangement of objects and a location for Planet X following predefined logic rules.