Unity_3DTopDown_LookAtMouse

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class LookAtMouse : MonoBehaviour
{
    Camera MainCam;

    private void Start()
    {
        //Unity allows us to assign the main camera by a MainCamera tag
        MainCam = Camera.main; //same as FindGameObjectsWithTag
    }


    void Update()
    {
        /*1.) First thing you need to know is that the mouse and the character is not on the same grid.
         * The mouse is in screen space, the character in world space */

        //Instead of using an ray to bring the mouse into the world, we can just check the characters screen space
        Vector3 ViewportPos = MainCam.WorldToScreenPoint(this.transform.position);

        /*2.) Now we need to use offset, you learn this in school alonsgide Pythagoras theorem,
         * because that is how you get the length of the vector and direction */
        Vector3 offset = Input.mousePosition - ViewportPos; // Offset is the difrince in vector space
        //The Unity normalized function uses the theorem to find the distance and then devides the vector with it
        Vector3 EulerDirection = offset.normalized;

        //There is just one little problem, this works for 2D space not 3D, we need the Y as the Z
        EulerDirection = new Vector3(EulerDirection.x, 0, EulerDirection.y);//fixed it just like that

        //3.) Now that we have the direction we just set the rotation to look in that direction
        this.transform.rotation = Quaternion.LookRotation(EulerDirection);
    }
}