Unity : CameraNavigation

CameraNavigation.cs

using UnityEngine;
using System.Collections;

public class CameraLook : MonoBehaviour {
    float minFov;
    float maxFov;
    float sensitivity;

    int boundary; // distance from edge scrolling starts
    int speed;

    private int screenWidth;
    private int screenHeight;

    // Use this for initialization
    void Start()
    {
        minFov = 15f;
        maxFov = 90f;
        sensitivity = 50f;

        boundary = 50;
        speed = 20;
        screenWidth = Screen.width;
        screenHeight = Screen.height;
    }

    // Update is called once per frame
    void Update()
    {
        float fov = Camera.main.fieldOfView;
        fov -= Input.GetAxis("Mouse ScrollWheel") * sensitivity;
        fov = Mathf.Clamp(fov, minFov, maxFov);
        Camera.main.fieldOfView = fov;
        Vector3 position = transform.position;

        if (Input.mousePosition.x > screenWidth - boundary && Input.mousePosition.x < screenWidth)
        {
            position.x += speed * Time.deltaTime;
        }

        if (Input.mousePosition.x < 0 + boundary && Input.mousePosition.x >= 0)
        {
            position.x -= speed * Time.deltaTime;
        }

        if (Input.mousePosition.y > screenHeight - boundary && Input.mousePosition.y < screenHeight)
        {
            position.z += speed * Time.deltaTime;
        }

        if (Input.mousePosition.y < 0 + boundary && Input.mousePosition.y >= 0)
        {
            position.z -= speed * Time.deltaTime;
        }

        transform.position = position;
    }

    void OnGUI()
    {
        GUI.Box(new Rect((Screen.width / 2) - 140, 5, 280, 25), "Mouse Position = " + Input.mousePosition);
        GUI.Box(new Rect((Screen.width / 2) - 70, Screen.height - 30, 140, 25), "Mouse X = " + Input.mousePosition.x);
        GUI.Box(new Rect(5, (Screen.height / 2) - 12, 140, 25), "Mouse Y = " + Input.mousePosition.y);
    }
}