Unity - Camera Shift By Borders (Desktop)

//Global variables
    private const float STRAFE_SCALE = 0.1f;
    private Rect movingRect;
    private const float MAX_DISTANCE = 1400f;
    float distance = 200f;

    void Start ()
        {
            float w = Screen.width * 0.6f;
            float h = Screen.height * 0.7f;

            movingRect = new Rect ((Screen.width - w) / 2f, (Screen.height - h) / 2f, w, h);
            //...
        }

    void Update ()
        {
                Quaternion rotation = Quaternion.Euler (40f, rotationX, 0);

              float movingX = 0.0f;
                float movingY = 0.0f;
                Vector3 mouse = Input.mousePosition;

                //Bound Camera Strafe
                if (mouse.x > movingRect.xMax)
                    movingX += STRAFE_SCALE * (mouse.x - movingRect.xMax);
                else if (mouse.x < movingRect.xMin)
                    movingX += STRAFE_SCALE * (mouse.x - movingRect.xMin);
                else
                    movingX = 0;

                if (mouse.y > movingRect.yMax)
                    movingY += STRAFE_SCALE * (mouse.y - movingRect.yMax);
                else if (mouse.y < movingRect.yMin)
                    movingY += STRAFE_SCALE * (mouse.y - movingRect.yMin);
                else
                    movingY = 0;

                tran += rotation * new Vector3 (movingX, 0, movingY);
                tran.y = 0f;
                tran.x = Mathf.Clamp (tran.x, -MAX_DISTANCE, MAX_DISTANCE);
                tran.z = Mathf.Clamp (tran.z, -MAX_DISTANCE, MAX_DISTANCE);

                //...

                Vector3 dist = rotation * new Vector3 (0, 0, -distance);

                transform.rotation = rotation;
                transform.position = GetSmoothedHeightAt (tran) + dist;
        }