From the campaign:
I designed Dark from the ground up to cultivate the tension and suspense of stealth gameplay. For the players, the game hinges on regular playing cards, rather than dice. This allows players to better plan, make both dramatic and tactical choices, and benefit from patience and precision in tangible ways. The better hidden your character, the more cards you have in hand.
Characters themselves are described by the cards players place in their deck and the skills they train. Each player needs their own deck of regular playing cards to play.