Rotate sprite towards mouse

RotateSpriteTowardsMouse.cs

// Rotate sprite/object towards mouse
// Reference: http://johnstejskal.com/wp/rotating-objects-and-sprites-in-unity3d-using-cs-c/
// https://forum.unity3d.com/threads/how-to-detect-angle-from-one-object-to-another-in-2d.477510/
// Usage: Attach this script to sprite, use Orthographic camera!

using UnityEngine;
using System.Collections;

public class RotateSpriteTowardsMouse : MonoBehaviour 
{

	private Camera cam;

	void Start () 
	{
		cam = Camera.main;
	}
	

	void Update () 
	{
		Vector3 mousePos = cam.ScreenToWorldPoint(Input.mousePosition);
		
		// rotate Y (green axis) towards mouse
		//transform.rotation = Quaternion.LookRotation(Vector3.forward, mousePos - transform.position);

		// rotate Y (green axis) away from mouse
		//transform.rotation = Quaternion.LookRotation(Vector3.forward, transform.position-mousePos);

		// rotate X (red axis) towards mouse
		Vector3 perpendicular = Vector3.Cross(transform.position-mousePos,Vector3.forward);
		transform.rotation = Quaternion.LookRotation(Vector3.forward, perpendicular);

		// rotate X (red axis) away from mouse
		//Vector3 perpendicular = Vector3.Cross(mousePos-transform.position,Vector3.forward);
		//transform.rotation = Quaternion.LookRotation(Vector3.forward, perpendicular);
		
		// using lookat
    	        // transform.LookAt(target.position, new Vector3(0, 0, -1));
		
		// can also set transform.up (green axis)
		//mousePos.z = 0;
		//transform.up = mousePos - transform.position;
	}
}