Fixing object position within range

Hi,

I'm working on a feature where you can mouse-pan the camera across a scene. The idea is that you cannot pan outside of the scene. There are currently 2 issues:

1) You can still pan along the x-direction and go outside the bounds (meaning the bounds are calculated incorrectly)

2) If I resize the screen, the bounds are the wrong size.

My logic for boundaries was this: if the next pan goes outside the boundary, cancel.

Here's my code, I don't know where I pulled the number 5 out of but it worked for that current screen size, and that's the problem. But I don't know what the calculation should be.

 using UnityEngine;
 using System.Collections;
 
 public class ZoomPan : MonoBehaviour
 {
 
     public float moveSensitivityX = 1.0f;
     public float moveSensitivityY = 2.0f;
     public bool updateZoomSensitivity = false;
     public float orthoZoomSpeed = 1.0f;
     public float minZoom = 10.0f;
     public float maxZoom = 40.0f;
     public bool invertMoveX = false;
     public bool invertMoveY = false;
     public float zoomMultiplier = 1f;
     
     private bool isPanning = false;
     
     private float boundaryBottom;
     private float boundaryTop;
     private float boundaryLeft;
     private float boundaryRight;
     
     void Start()
     {
         maxZoom = 80f / Screen.width * Screen.height / 2.0f;
         Camera.main.orthographicSize = maxZoom;
         boundaryBottom = Camera.main.transform.position.y - 5;
         boundaryTop = Camera.main.transform.position.y + 5;
         boundaryLeft = Camera.main.transform.position.x - 5;
         boundaryRight = Camera.main.transform.position.x + 5;
     }
     
     private Vector2 startPanPos;
     
     void Update()
     {
         
         //checkNotOutsideBounds();
         
         if(updateZoomSensitivity)
         {
             moveSensitivityX = Camera.main.orthographicSize / 10.0f;
             moveSensitivityY = Camera.main.orthographicSize / 5.0f;
         }
         
         if(!isPanning && Input.GetMouseButton(0)) //start panning
         {
             //Debug.Log("Panning");
             isPanning = true;
             startPanPos = Input.mousePosition;
         }
         else if(isPanning && !Input.GetMouseButton(0)) //stop panning
         {
             //Debug.Log("Not panning");
             isPanning = false;
         }
         else if(isPanning && Input.GetMouseButton(0)) //panning
         {
             
             Vector2 delta = new Vector2(Input.mousePosition.x - startPanPos.x, Input.mousePosition.y - startPanPos.y);
             float posX = delta.x * moveSensitivityX * zoomMultiplier * Time.deltaTime;
             posX = invertMoveX ? posX : -posX;
             
             float posY = delta.y * moveSensitivityY * zoomMultiplier * Time.deltaTime;
             posY = invertMoveY ? posY : -posY;
             
             Debug.Log(Camera.main.transform.position.x + "," + Camera.main.transform.position.y + "," + Camera.main.transform.position.z + " --> clamped within " + boundaryBottom + "|" + boundaryTop + ", " + boundaryLeft + "|" + boundaryRight);
             Vector3 newPosition = Camera.main.transform.position + new Vector3(posX, posY, posX);
             
             bool canPan = true;
             
             if(zoomMultiplier == 1f)
             {
                 if(Screen.width > Screen.height)
                 {
                     posY = 0; //clamp y-movement
                     
                 }
                 else
                 {
                     posX = 0; //clamp x-movement
                 }
                 if(newPosition.x < boundaryLeft || newPosition.x > boundaryRight)
                     canPan = false;
                 if(newPosition.y < boundaryBottom || newPosition.y > boundaryTop)
                     canPan = false;
             }
             if(canPan)
                 Camera.main.transform.position = newPosition;
             startPanPos = Input.mousePosition;
             
         }
         else if(Input.GetAxis("Mouse ScrollWheel") > 0f) //zoom in
         {
             //Debug.Log("Zoom in");
             Camera.main.orthographicSize -= orthoZoomSpeed;
             Camera.main.orthographicSize = Mathf.Clamp(Camera.main.orthographicSize, minZoom, maxZoom);
             zoomMultiplier = Camera.main.orthographicSize / maxZoom;
             
  
         }
         else if(Input.GetAxis("Mouse ScrollWheel") < 0f) //zoom out
         {
             //Debug.Log("Zoom out");
             Camera.main.orthographicSize += orthoZoomSpeed;
             Camera.main.orthographicSize = Mathf.Clamp(Camera.main.orthographicSize, minZoom, maxZoom);
             zoomMultiplier = Camera.main.orthographicSize / maxZoom;
             
         }
         
     }
     
 }

In the image, you can see both issues. I cannot pan any further up (there's a margin of the same size around the whole of the checkered square), and also the boundary has been incorrectly calculated on the x-axis. If my screen was larger in height than width, I would assume the boundary on the y-axis would be incorrectly calculated instead.