Coin Birds is an idle game. You buy birds and they lay eggs. You can sell the eggs for coins with which you can either buy more birds or withdraw money. However, to withdraw money either you or your referees have to invest money! Coin Birds doesn't show any ads or whatsoever, so the only source of money are the investments of the users - in other words, it is a ponzi scheme.
It's time to get your Invitation.codes account too 😎