1. A method comprising: receiving, by a game server, from a client computer input entered by a user during a session of an online slots game, the input defined to spin wheels of the online slots game, the game server being part of a plurality of games servers configured to interface with a plurality of clients over a network for playing the online slots game; defining an initial tier and one or more additional tiers for play of the online slots game, each tier being assigned an odds value that changes with each assigned tier, and each tier is defined to have a set of spins; assigning, by the game server, the initial tier when the user begins playing the online slots game; assigning, by the game server, tiers with changed odds when an option to play a bonus game is not presented during the set of spins for each tier; and assigning, by the game server, the initial tier upon determining that the bonus game was played during the session, wherein the operations of the method are executed by a processor.