This paper investigates if real-time biofeedback can be used to enhance individual player experience by increasing the sense of flow and immersion with the player and to what extent this can be achieved. We used an oximeter, the Contec CMS50D+ to capture live biometric data which was in turn interpreted and implemented in the game Half-Life 2. The data was used to alter the damage taken and inflicted by the player, the timescale and the field of view, all to enhance the players sense of flow and immersion. An experiment group playing the modification and a control group playing the original game were evaluated, whose test results were compared to one another to analyze the alterations. The test subjects filled out a game experience questionnaire customized to this game and research, and were lastly interviewed. While the results indicate that it is possible to enhance gameplay experience by using biometric data, further research is needed in order to conclude to what extent this is possible.