ce = maxEngineForce
          else if (this.keys.s) engineForce = -maxEngineForce
          else engineForce = 0

          // left/right
          if (this.keys.a) {
            if (this.vehicleSteering < steeringClamp) this.vehicleSteering += steeringIncrement
          } else if (this.keys.d) {
            if (this.vehicleSteering > -steeringClamp) this.vehicleSteering -= steeringIncrement
          } else {
            if (this.vehicleSteering > 0) this.vehicleSteering -= steeringIncrement / 2
         