The paper explores defining and measuring immersion in games through three experiments. Experiment 1 found that participants who played an immersive game took longer to switch to a non-game task than controls. Experiment 2 found higher immersion and different eye movements in an immersive game versus a non-immersive one. Experiment 3 showed that interaction pace affected immersion, anxiety, and other emotions. Overall, the research suggests immersion involves loss of awareness of time and reality and correlates with engagement measures like flow and cognitive absorption.