In recent years, indoor or at-home sports have experienced significant growth. However, monotony is a common challenge in these static physical activities. Exergames, a genre of video games that combines physical activity and entertainment, have emerged as an attractive solution. Nevertheless, running on a treadmill and engaging in other activities simultaneously presents additional challenges. The balance and concentration required during running while interacting with a video game demand a special focus on the design of the Exergame. This paper presents a mobile Exergame designed specifically for treadmill running, utilizing interaction with a smartwatch. The game offers natural environments where, through smartwatch technology, it interprets the player's movements, transforming them into running speed and interactive actions by detecting gestures within the game. The main objective is to provide users with a satisfying gaming experience tailored to the characteristics of treadmill running. Particular emphasis has been placed on prioritizing the playful component of this Exergame, recognizing its relevance in the context of treadmill running. To evaluate the achievement of objectives and the proposed hypothesis, a comparative study was conducted between the proposed Exergame and a treadmill running simulator. Participants experienced both experiences and subsequently completed the Game Experience Questionnaire (GEQ), specifically the In-game GEQ version. The results obtained indicate that participants had a better gaming experience in the Exergame than in the simulator. These findings highlight the importance of prioritizing the playful component in Exergames and provide guidelines for future improvements and developments in the field.