FLEET is a free ship-design simulator that reaches students in their native environment--video games. It is also a physics simulator that applies content first learned through hands-on scientific investigations. Using FLEET, students design and use ships for various naval missions by mastering scientific concepts such as force, energy, and work, while employing an engineering design process. This article describes the use of FLEET in traditional physics classrooms in the early high school years, although FLEET is being used in elementary and middle schools and in more advanced academic settings. The gameplay is intuitive, and teachers have found students need little support to get started with this physics simulator.