Unity editor style camera script

Hi guys,

I'm making a creation type game, and I want my in-game camera to behave exactly like the "camera" does in the editor. This means the following features:

• Scrolling the middle wheel will zoom in and out

• Holding down the middle wheel and moving the mouse will pan the screen

• Pressing the right button will rotate the camera while it is pressed

• The arrow keys will move the camera forward, left, right and back. The longer these keys are pressed, the faster the camera will move exponentially

How would I go about doing this? I managed to procure a script to pan and zoom, but it requires an object in focus, which isn't what the scene camera does:

 using UnityEngine;
 using System.Collections;
 
 public class CameraMovement : MonoBehaviour
 {
     public Transform target;
     public Vector3 targetOffset;
     public float distance = 5.0f;
     public float maxDistance = 20;
     public float minDistance = .6f;
     public float xSpeed = 200.0f;
     public float ySpeed = 200.0f;
     public int yMinLimit = -80;
     public int yMaxLimit = 80;
     public int zoomRate = 40;
     public float panSpeed = 0.3f;
     public float zoomDampening = 5.0f;
 
     private float xDeg = 0.0f;
     private float yDeg = 0.0f;
     private float currentDistance;
     private float desiredDistance;
     private Quaternion currentRotation;
     private Quaternion desiredRotation;
     private Quaternion rotation;
     private Vector3 position;
 
     void Start() { Init(); }
     void OnEnable() { Init(); }
 
     public void Init()
     {
         //If there is no target, create a temporary target at 'distance' from the cameras current viewpoint
         if (!target)
         {
             GameObject go = new GameObject("Cam Target");
             go.transform.position = transform.position + (transform.forward * distance);
             target = go.transform;
         }
 
         distance = Vector3.Distance(transform.position, target.position);
         currentDistance = distance;
         desiredDistance = distance;
 
         //be sure to grab the current rotations as starting points.
         position = transform.position;
         rotation = transform.rotation;
         currentRotation = transform.rotation;
         desiredRotation = transform.rotation;
 
         xDeg = Vector3.Angle(Vector3.right, transform.right);
         yDeg = Vector3.Angle(Vector3.up, transform.up);
     }
 
     /*
      * Camera logic on LateUpdate to only update after all character movement logic has been handled. 
      */
     void LateUpdate()
     {
         // If Control and Alt and Middle button? ZOOM!
         if (Input.GetMouseButton(2) && Input.GetKey(KeyCode.LeftAlt) && Input.GetKey(KeyCode.LeftControl))
         {
             desiredDistance -= Input.GetAxis("Mouse Y") * Time.deltaTime * zoomRate * 0.125f * Mathf.Abs(desiredDistance);
         }
         // If middle mouse and left alt are selected? ORBIT
         else if (Input.GetMouseButton(2) && Input.GetKey(KeyCode.LeftAlt))
         {
             xDeg += Input.GetAxis("Mouse X") * xSpeed * 0.02f;
             yDeg -= Input.GetAxis("Mouse Y") * ySpeed * 0.02f;
 
             ////////OrbitAngle
 
             //Clamp the vertical axis for the orbit
             yDeg = ClampAngle(yDeg, yMinLimit, yMaxLimit);
             // set camera rotation 
             desiredRotation = Quaternion.Euler(yDeg, xDeg, 0);
             currentRotation = transform.rotation;
 
             rotation = Quaternion.Lerp(currentRotation, desiredRotation, Time.deltaTime * zoomDampening);
             transform.rotation = rotation;
         }
         // otherwise if middle mouse is selected, we pan by way of transforming the target in screenspace
         else if (Input.GetMouseButton(2))
         {
             //grab the rotation of the camera so we can move in a psuedo local XY space
             target.rotation = transform.rotation;
             target.Translate(Vector3.right * -Input.GetAxis("Mouse X") * panSpeed);
             target.Translate(transform.up * -Input.GetAxis("Mouse Y") * panSpeed, Space.World);
         }
 
         ////////Orbit Position
 
         // affect the desired Zoom distance if we roll the scrollwheel
         desiredDistance -= Input.GetAxis("Mouse ScrollWheel") * Time.deltaTime * zoomRate * Mathf.Abs(desiredDistance);
         //clamp the zoom min/max
         desiredDistance = Mathf.Clamp(desiredDistance, minDistance, maxDistance);
         // For smoothing of the zoom, lerp distance
         currentDistance = Mathf.Lerp(currentDistance, desiredDistance, Time.deltaTime * zoomDampening);
 
         // calculate position based on the new currentDistance 
         position = target.position - (rotation * Vector3.forward * currentDistance + targetOffset);
         transform.position = position;
     }
 
     private static float ClampAngle(float angle, float min, float max)
     {
         if (angle < -360)
             angle += 360;
         if (angle > 360)
             angle -= 360;
         return Mathf.Clamp(angle, min, max);
     }
 }

Thanks in advance