Planet Unknown is a competitive game for 1-6 players in which players attempt to develop the best planet. Each round, each player places one polyomino-shaped, dual-resource tile on their planet. Each resource represents the infrastructure needed to support life on the planet. Every tile placement is important to cover your planet efficiently and also to build up your planet's engine. After placing the tile, players do two actions associated with the two infrastructure types on the tile. Some tile placements trigger "meteors" that make all planets harder to develop and prevent them from scoring points in the meteor's row and column.