How to I mouse Drag sprite diagonally only?

Been trying the whole day today, but i still couldnt figure out. i think i only need to change the code onMousedrag but i do not know how.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class FirstPart : MonoBehaviour
 {
     [SerializeField]
     private Transform redPlace;
 
     private Vector2 initialPosition;
 
     private Vector2 mousePosition;
 
     private float deltaX, deltaY;
 
     public static bool locked;
 
     
 
     void Start()
     {
         initialPosition = transform.position;
     }
 
     private void OnMouseDown()
     {
         if (!locked)
         {
             deltaX = Camera.main.ScreenToWorldPoint(Input.mousePosition).x - transform.position.x;
             deltaY = Camera.main.ScreenToWorldPoint(Input.mousePosition).y - transform.position.y;
         }
     }
 
     private void OnMouseDrag()
     {
         
         if (!locked)
         {
             mousePosition = Camera.main.ScreenToWorldPoint(Input.mousePosition);
              transform.position = new Vector2(mousePosition.x - deltaX, mousePosition.y - deltaY);
     
         }
 
     }
 
     private void OnMouseUp()
     {
         if (Mathf.Abs(transform.position.x - redPlace.position.x) <= 0.5f &&
                    Mathf.Abs(transform.position.y - redPlace.position.y) <= 0.5f)
         {
             transform.position = new Vector2(redPlace.position.x, redPlace.position.y);
             locked = true;
         }
         else
         {
             transform.position = new Vector2(initialPosition.x, initialPosition.y);
         }
     }
 
 }