Competition is a major motivator for game players. In this paper, we quantify and analyze how competition affects the players' degree of immersion and engagement in the mobile social game Cookie Run. Specifically, we quantify the level of competition by the relative score difference between the player and their competitor. We measure the level of immersion by the length of game time; and we measure the level of engagement by the number of paid score-boosting items. We found that users are much more immersed and engaged as the competition increases, and the effect is greater in high-level players.