The players have to coordinate in physical space in order to complete a task. Co-locality presupposes a multiplayer game.
With co-locality the players have to physically be present and in proximity to each other in a predefined location in order to jointly carry out a game action. A real world example of this is the Two-man rule, a security feature of nuclear missile launch sites.
The opposite implementation is also possible. In this case, players would have to avoid to come too close to each other.
Additionally, co-locality can amplify the spatial structure of a game, especially if the location where the it occurs is predefined and has meaning in the context of a narrative.
Co-locality can be implemented as a case of balance cooperation and competition. Players would then enter a temporary cooperation in order to pursue a common goal.
Co-locality might involve the combination of digital object in the possession of different players. It could be about the creation of a map from distinct parts.
Another example is the combination of different abilities of players with different roles. In the context of the co-locality pattern, they might need to be physically close in order to combine their abilities.