Referral codes is a elaborate system constructed by Battle Camp. This system rewards players for inviting people to play the game. Players will receive gifts by giving the new player a referral code. New players are given one and only one opportunity to enter a referral code, which appears when reaching level 5. New players joining through an invite via Facebook will automatically receive a the reward. Players can locate their referral code by going to their settings under the 'Me' button.
A code you could use :