screen pos and unlit

Shader "Unlit/ScreenPos"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // make fog work
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
                
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                //UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
                float4 pos : TEXCOORD1;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                //UNITY_TRANSFER_FOG(o,o.vertex);

                o.pos = ComputeScreenPos(o.vertex);

                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                // sample the texture
                //i.pos.y = 1 - i.pos.y;
                float2 uvv = i.pos.xy/i.pos.w;
                fixed4 col = tex2D(_MainTex, uvv);

                col.g *= step(0.5,frac(10*(i.uv.x+i.uv.y+_Time.x)));
                col.b *= step(0.5,frac(10*(i.uv.x+i.uv.y+_Time.x)));
                //col.r=0;
                // apply fog
                //UNITY_APPLY_FOG(i.fogCoord, col);
                return col;
            }
            ENDCG
        }
    }
}