A system, a machine-readable storage medium storing instructions, and a computer-implemented method are described herein for a System Tuner for customizing a player's experience. The System Tuner creates an optimal game model based on game-related data of a plurality of players. The optimal game model corresponds to a player segment in the plurality of players. The System Tuner generates one or more rules for building a game variant based on the optimal game model. The System Tuner detects a first player accessing the game. The System Tuner determines a particular player segment to which the player belongs. The System Tuner generates a game variant based on an optimal game model for the particular player segment and sends the game variant to a client device.