Tinder is currently the world’s hottest dating app with millions of users who participate in billions of interactions. Why is it addicting? It’s designed to be that way...

...The most addictive part of the game by far is its multiplayer. 4 players team up against waves of enemies at different difficulties...To unlock weapons, gear, powers and experience in multiplayer, the players must buy random packs which contain different kinds of cards...The expectation of trying to unlock a black card is unbelievably addicting.