Serious games have unique strengths that can be used to augment science education. For the current study, we developed and investigated a serious game to assess kindergartners’ discovery of the laws of physics in the so-called Hippo app. The participants were 71 children, aged 5 years and 5 months on average. The app consisted of three game-plays: slides, seesaw, and pendulum. Children were asked to set variables (such as the steepness of the slide) correctly in order to provide a hungry hippo with a drink or some food. Children’s gaming behavior was assessed via exploration and efficiency scores, and next related to executive control, nonverbal reasoning, and vocabulary. Exploration was defined as the number of actions corrected for the total playing time, efficiency as the number of correctly solved problems corrected for the total number of attempts. The results revealed that efficiency and exploration scores did not correlate significantly, indicating two distinct types of gaming behaviors. Both types were associated with attentional control. Mediation analysis showed that the relation between exploration and attentional control was mediated by vocabulary, while the relation between efficiency and attentional control was mediated by nonverbal reasoning. To conclude, kindergartners’ efficiency and exploration can be seen as independent game behaviors; both demanding attentional control, but mediated by verbal skills in the case of exploration and by nonverbal reasoning in the case of efficiency.