setRandomState() {
    // The control-theory state variables of the cart-pole system.
    // Cart position, meters.
    this.x = Math.random() - 0.5;
    // Cart velocity.
    this.xDot = (Math.random() - 0.5) * 1;
    // Pole angle, radians.
    this.theta = (Math.random() - 0.5) * 2 * (6 / 360 * 2 * Math.PI);
    // Pole angle velocity.
    this.thetaDot =  (Math.random() - 0.5) * 0.5;
  }
Set the state of the cart-pole system randomly.