Digital exercise games (exergames) can motivate players to carry out physical exercises. However, most exergames are controlled by confined and predefined movements and do not promote long-term motivation. Well-funded commercial games often excel at long-term motivation, but are not operated with motion input. We choose the best of both worlds by turning an existing videogame without motion control into an exergame. By adding motion-based controls and a feedback overlay to the popular firstperson action game Portal 2, and designing custom game levels around exercise regimens with the freely available Hammer editor, we turned it into the exergame Sportal. This approach can give gamers an incentive to exercise using high quality first-person gameplay and it can potentially acquaint exerciseeager non-gamers with a popular videogame title.