Simple Map Movement (Pan, Rotate, Zoom)

//Attach to an Empty GameObject, With Your camera as a child

using UnityEngine;
using System.Collections;

public class MapCamera : MonoBehaviour {
    public float panSpeed = 0.5f;
    public KeyCode panKey = KeyCode.None;
    public bool invertPanX = true;
    public bool invertPanY = true;

    public float rotateSpeed = 2;
    public KeyCode rotateKey = KeyCode.LeftControl;
    public bool invertRotateX = true;
    public bool invertRotateY = false;

    public float zoomSpeed = 1;
    public bool useMouseWheel = true;
    public KeyCode zoomKey = KeyCode.LeftShift;
    public bool invertZoom = false;

    private bool _isDragging;
    private Vector2 lastMousePos;
    private Transform t;
    private Camera c;

    public bool IsCameraBeingDragged {
        get { return _isDragging; }
    }

    void Start () {
        t = transform;
        c = GetComponentInChildren<Camera>();
    }
    // Update is called once per frame
    void Update () {
        //When clicking the mouse down
        if(Input.GetMouseButtonDown(0)) {
            _isDragging = true;
            lastMousePos = Input.mousePosition;
        }

        //While dragging
        if(Input.GetMouseButton(0)) {
            Vector2 mousePos = Input.mousePosition;
            if(rotateKey != KeyCode.None && Input.GetKey(rotateKey)) {
                t.Rotate(new Vector3((mousePos.y - lastMousePos.y) * (invertRotateY?-1:1), (mousePos.x - lastMousePos.x) * (invertRotateX?-1:1), 0) * Time.deltaTime * rotateSpeed, Space.Self);
                t.localRotation = Quaternion.Euler(new Vector3(t.localRotation.eulerAngles.x, t.localRotation.eulerAngles.y, 0));
            } else if(zoomKey != KeyCode.None && Input.GetKey(zoomKey)) {
                c.transform.Translate(c.transform.forward * (mousePos.y - lastMousePos.y) * (invertZoom?-1:1) * Time.deltaTime * zoomSpeed);
            } else if(panKey == KeyCode.None || Input.GetKey(panKey)) {
                t.Translate(new Vector3((mousePos.x - lastMousePos.x) * (invertPanX?-1:1), 0, (mousePos.y - lastMousePos.y) * (invertPanY?-1:1)) * Time.deltaTime * panSpeed);
            }
            lastMousePos = Input.mousePosition;
            //c.transform.LookAt(t);
        }

        //When releasing the mouse
        if(Input.GetMouseButtonUp(0)){
            _isDragging = false;
        }

        if(Input.GetAxis("Mouse ScrollWheel") != 0) {
            c.transform.Translate(c.transform.forward * Input.GetAxis("Mouse ScrollWheel") * (invertZoom?-100:100) * Time.deltaTime * zoomSpeed);
        }
    }
}