Each of two players operates a food truck, and must allocate 30 minutes between preparing burgers and preparing fries. Payoff is equal to whichever is smaller: the number of fries or the number of burgers brought on the truck. By default, one player has an absolute advantage in the production of both, but the players differ in opportunity cost.
When you allow trade, each player can propose trading burgers for fries. Because players differ in opportunity cost, there are mutually beneficial trades.
With this game, your students experience first-hand the linear production model, and learn that opportunity-cost differences lead to gains from trade.