Picture two rival coffee shops on the same street. Each one must decide whether to run a half‑price promotion next week. If both discount, they barely break even. If neither discounts, both earn healthy profits. But if one discounts while the other doesn’t, the discounter steals customers and the other loses big. This isn’t just a pricing puzzle — it’s a game. Game theory helps us predict what rational players will do and how they can avoid destructive competition over time.