This webpage uses the Runge-Kutta-Fehlberg fourth-order method with fifth-order error checking (RKF45) to approximate the solution to the problem of the Duffing oscillator: $$\ddot{x} + \delta \dot{x} + \alpha x + \beta x^3 = \gamma \cos{(\omega t)}$$ Below you can specify these various parameters, as well as the initial conditions and starting and end times. The default values give chaotic behaviour.