Cournot Duopoly: Quantity Competition & Nash Equilibrium

This simulator renders the classic Cournot duopoly model in 3D: two firms simultaneously choose output quantities, a single linear demand curve sets the market-clearing price, and each firm earns a profit that depends on both its own and its rival's output. The green mesh is Firm 1's full profit surface π₁(q₁,q₂) over the quantity plane, with a marker ball tracking the current outcome. Two reaction curves show each firm's best response to any quantity the other might choose, and their intersection — highlighted in gold — is the Cournot-Nash equilibrium. Run the best-response dynamics button to watch both firms alternately adjust toward that equilibrium, tracing a spiral path across the floor exactly as the reaction functions predict.