Question 2d Object relative rotation with mouse drag.

Hi guys. First of all sorry for my worse English.

I try to make rotate a sprite with mouse drag. I can do it. The script is at below. But the problem is when mouse button down the sprite rotates immediately to the mouse position. I want a rotation with relative to mouse position. I dont want to chase mouse position.

Thanks a lot.

Code (CSharp):

1.  
2. private void Update()
3.     {
4.    
5.  
6.        
7.         pos = Camera.main.WorldToScreenPoint(transform.position);
8.  
9.         dir = Input.mousePosition - pos;
10.         angle = Mathf.Atan2(dir.y, dir.x) * Mathf.Rad2Deg;
11.  
12.         if (Input.GetMouseButton(0))
13.         {
14.            
15.            
16.  
17.                transform.rotation = Quaternion.AngleAxis(angle, Vector3.forward);
18.  
19.            
20.  
21.         }
22.  
23.      
24.     }

 

You would store the position of the mouse when it is first pressed and then calculate the rotation based on how much it has moved while the button is held.

 

I cant do it

 

What have you tried?