MIT lecturer Ian Ball covers zero-sum games in this session from 14.12 Economic Applications of Game Theory. He defines zero-sum games as strictly competitive settings where one player's gain is exactly another's loss, using checkers and chess as running examples. The lecture works through the formal structure of such games, how payoffs are represented, and why the complete conflict of interest simplifies certain strategic predictions compared to general games. Ball builds up the mathematical tools students need to analyze optimal play and equilibrium behavior in these settings, connecting the abstract game-theoretic framework back to concrete board games so the logic stays grounded. Part of MIT's fall 2025 offering of 14.12, released through MIT OpenCourseWare under a Creative Commons license, running about eighty minutes.