Chillverse's Referral program lets you invite friends and earn diamonds together. Your Referral page gives you a personal invite link built around your own referral code — share it with a friend, and when they sign up through that link, they're automatically linked to you as their referrer.
The reward triggers once your friend plays their very first game after signing up — at that point, you both receive a diamond bonus. This only pays out once per friend, so there's no way to farm rewards from the same person twice, and it doesn't matter which game they choose to play first.