Invite friends to play challenges. Gamers can issue private challenges for Overwatch, Fortnite, Call of Duty, Dota 2, Rocket League and many more. Winners earn bragging rights and rewards. With Zark, you have access to your own private community in the gaming world. You set the rules, issue challenges, determine winners, and collect rewards. Connect with friends, issue challenges, earn credits and redeem in-app for digital gift cards.