A wagering game system and method include a skill-based bonus game for a game of chance that enables a player to win a bonus prizes, the bonus game having a bonus prize input device configured to be manipulated by the player to perform a task having an outcome that determines the bonus prize. A processor adjusts difficulty of performing the task based upon a historical skill level of the player. The processor also adjusts the historical skill level of the player based on various parameters such as prize history, wagering history, and percentage returned to the player.