Methods, systems, and computer programs are presented for adjusting bonus winning odds while playing an online slots game. One method includes an operation for receiving user input during a session of an online slots game, where the user input is defined to spin wheels of the online slots game. In addition, the method includes an operation for defining an initial tier and one or more additional tiers for play of the online slots game during the session, each tier being assigned an odds value that changes with each assigned tier, and each tier being defined to have a set of spins. Further, the method includes operations for assigning tiers with changed odds when an option to play a bonus game is not presented during the predefined set of spins for each tier, and for assigning the initial tier upon determining that the bonus game was played during the session.