Methods, systems, and computer programs are presented for adjusting bonus winning odds while playing an online slots game. A server is configured to provide access to remote users having user accounts for playing the online slots game over a network connection and is configured to establish a plurality of tiers for playing the online slots game that includes turns. Each tier is assigned an odds value for winning a chance to play a bonus game that is different from the online slots game. The method enables play of each turn, wherein chances to win the bonus game at each turn are based a selected tier. The method includes presenting to the graphical user interface images associated with the bonus game when a player wins the chance to play the bonus game during a turn, and presenting to the graphical user interface options to send challenge bonus game to a friend. Play by the friend of the sent challenge game adds to winnings of said bonus game to the player. The method includes presenting to the graphical user interface graphics associated with the online slots game after completion of the bonus game.