ESP is a tile placement game of strategy, deduction and extrasensory perception. Each player gets two sets of tiles with the five standard Zener symbols used in ESP testing, and attempts to be the first to make a row of 5 different symbols. Initially, the tiles can be placed face-up or face-down; in the later stages of the game, a player may flip a face-down tile or move a face-up tile. Inferring the identity of an opponent's face-down tiles is a vital part of the game.