The game is a 2 to 4 player trick-taking card game using a deck of 25 custom cards. From the publisher's website: Parallel Worlds has a unique playing deck consisting of 25 cards, made up of four 6 card suits belonging to the elements Earth, Air, Fire and Water, plus a Wild card. Each of the suits is also represented by a "House" name that originates from the 1,000's of planets spread throughout space and time. New Houses will be made available for collection and integration into any starter deck, enabling every player to customize their own deck to their personal taste. Before play commences each player can then select a complete 6 card suit from their own customized deck to represent them as "Temporal Adjuster" within the game.