Invisible city: Rebels vs. Spies is a location-based mobile game. It is to be played in a city by a party of 5-15 players. The aim is to visit locations in a city by playing a group game that engages you to interact with buildings, monuments, streets etc. The game has been designed and implemented by the Human-Computer Interaction Group of the University of Patras.

In order to play the game each player needs an internet-connected android-based mobile device. The content of the game is specific to the city of Patra in Greece. Other than that, it can be played everywhere if someone is interested in writing up the content and missions.

• Players. The players are either Rebels or Spies. Rebels try to win the game by successfully completing each round's assignment. Spies try to win the game by sabotaging the assignment.
• Assignments. The assignments are individual and last for one round. Some assignments are critical, some are not critical. The players are unaware whether the assignment is critical or not. An assignment is a simple location-related task. The player has to move to a specific location and perform a task. Tasks can be answer a location-specific question, perform an action etc. The player has a choice whether to perform the action correctly or not. The rest of the players won't know who performed correctly or not.
• Critical assignments. Critical assignments are crucial for the success of the revolution. If a critical assignment fails, the round is lost for the rebels. A player doesn't know whether his/her assignment is critical or not. There are always as many critical assignments as rebels.
• Rounds. The game is played in rounds. Each round starts with the leader selection: Each player votes and chooses a leader for the current round only. With every round a new leader selection happens. If all critical assignments of a round are successful, then the rebels win a base. Otherwise, if a critical assignment fails and the spies win a base.
• Leader. The leader's role is to give to each player the individual assignment for one round. The leader is the only one who knows which players get critical assignments and which non critical. After the leader completes the assignments, he/she continues to play as a regular player.
• Revelation. When most players want to, they can call for a special revelation vote after each round. There, they have to choose the players they suspect as being spies. If all spies are revealed, the game ends and the rebels win. If the revelation fails, the spies win another base.

• Christos Sintoris, Nikoleta Yiannoutsou, Demetriou Soteris, Nikolaos Avouris, 2013. Discovering the invisible city: Location-based games for learning in smart cities. Interaction Design and Architecture(s) Journal - IxD&A, 16

• http://www.invisiblecity.gr