Go, the board game.

Go is the oldest, continuously played board game in the world. Invented in China more than 2500 years ago and was once considered one of the four essential arts of the cultured aristocratic Chinese scholars in antiquity.

The number of legal board positions in Go has been calculated to be approximately 2.1 × 10¹⁷⁰, which is vastly greater than the number of atoms in the known, observable universe, estimated to be about 1 × 10⁸⁰

Despite the extreme complexity of the game, the rules of Go are relatively simple.