Unity shader learning (V) mouse moving box

According to the previous section , Created a square
Now let's move the box
The principle is very simple , Just make the central point of the square equal to the mouse position
Shader The code is as follows ：

Shader "Unlit/shader6"
{
     
    /// Mouse move square 
    Properties
    {
    
    _MouseCenter("MouseCenter",Vector)=(0,0,0,0)
    _RectColor("RectColor",Color)=(1,1,1,1)
    }
    SubShader
    {
    
        Tags {
     "RenderType"="Opaque" }
        LOD 100

        Pass
        {
    
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag


            #include "UnityCG.cginc"
        struct v2f{
    
            float4 vertex:SV_POSITION;
            float4 position:TEXCOORD1;
            float2 uv:TEXCOORD;
        };
        v2f vert(appdata_base v){
    
            v2f o;
            o.vertex=UnityObjectToClipPos(v.vertex);
            o.position=v.vertex;
            o.uv=v.texcoord;
            return o;
        }
        // Center point 
        float4 _MouseCenter;
        // Color 
        fixed4 _RectColor;
        // Draw a square 
        float rect(float2 pt,float2 size,float2 center){
    
            float2 p=pt-center;
            float2 halfsize=size*0.5;
            float hotz=step(-halfsize.x,p.x)-step(halfsize.x,p.x);
            float vert=step(-halfsize.y,p.y)-step(halfsize.y,p.y);
            return hotz*vert;
        }

            fixed4 frag (v2f i) : SV_Target
            {
    
                float2 pos=i.uv;
                float2 size=0.2;
                float inRect=rect(pos,size,_MouseCenter);
                fixed3 col=fixed3(1,1,0)*inRect;
                return fixed4(col,1.0);
            }
            ENDCG
        }
    }
}

Then just control _MouseCenter This parameter , adopt unity Script pair _MouseCenter Assign a value

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

public class MouseSquare : MonoBehaviour
{
    
   public Material mat;
    Vector4 mouse;
    Camera cam;
    void Start()
    {
    
        MeshRenderer rend = GetComponent<MeshRenderer>();
        mat = rend.material;
        mouse = new Vector4();
        mouse.z = Screen.height;
        mouse.w = Screen.width;
        cam = Camera.main;
    }

    // Update is called once per frame
    void Update()
    {
    
        RaycastHit hit;
        Ray ray = cam.ScreenPointToRay(Input.mousePosition);
        if (Physics.Raycast(ray,out hit))
        {
    
       
            mouse.x = hit.textureCoord.x;
            mouse.y = hit.textureCoord.y;
           // Debug.Log(hit.textureCoord);
            Debug.DrawLine(cam.transform.position, hit.point, Color.red);
        }
        mat.SetVector("_MouseCenter", mouse);
    }
}

Drag the script onto the object