The prevalence of obesity among adolescents and adults in the U.S. is a matter of concern. Exercise video games reach a wide audience and can be used to motivate increased physical activity. We have previously developed Astrojumper, an exergame exploring game mechanics that provide a fun experience and effective exercise, and have now developed a new version of Astrojumper that supports interval training through additional mechanics. We believe the new version will improve upon the first in player motivation, enjoyment and replayability, and also in the level of physical challenge the game affords its players.