豹式戰車
Nelson contributed the original concept of a tank combat game, which was inspired by Brand Fortner's Airfight, Jim Bowery's Spasim, and an unfinished tank game effort of Derek Ward. Nelson also provided the Panther tank artwork, the vehicle motion, view, and damage equations, and a significant fraction of the original code. John was a highly capable TUTOR IV programmer who created the overall game framework, providing key features such as team selection and messaging that turned the concept into a working game, later adding a number of refinements.