Camera border no work help!!

Script;
using UnityEngine;

public class CameraController : MonoBehaviour {

private bool doMovement = true;

public float panSpeed = 30f;
public float panBorderThickness = 10f;

public float scrollSpeed = 5;
public float minY = 10f;
public float maxY = 80;

void Update () {

    if (Input.GetKeyDown(KeyCode.Escape))
        doMovement = !doMovement;

    if (!doMovement)
        return;
	
    if (Input.GetKey("w") || Input.mousePosition.y >= Screen.height - panBorderThickness)
    {
        transform.Translate(Vector3.forward * panSpeed * Time.deltaTime, Space.World);
    }
    if (Input.GetKey("s") || Input.mousePosition.y <= panBorderThickness)
    {
        transform.Translate(Vector3.back * panSpeed * Time.deltaTime, Space.World);
    }
    if (Input.GetKey("d") || Input.mousePosition.x >= Screen.width - panBorderThickness)
    {
        transform.Translate(Vector3.right * panSpeed * Time.deltaTime, Space.World);
    }
    if (Input.GetKey("a") || Input.mousePosition.x <= panBorderThickness)
    {
        transform.Translate(Vector3.left * panSpeed * Time.deltaTime, Space.World);
    }

    float scroll = Input.GetAxis("Mouse ScrollWheel");

    Vector3 pos = transform.position;

    pos.y -= scroll * 1000 * scrollSpeed * Time.deltaTime;
    pos.y = Mathf.Clamp(pos.y, minY, maxY);

    transform.position = pos;
}

}

any solucion?