Load and overlay images over tiles with zoom scale and color fade

Shader "Infinity Code/Online Maps/Tileset With Overlay" 
{
    Properties 
    {
        _Color("Main Color", Color) = (1,1,1,1)
        _MainTex("Base (RGB) Trans (A)", 2D) = "white" {}
        _OverlayBackTex("Overlay Back Texture", 2D) = "black" {}
        _OverlayBackAlpha("Overlay Back Alpha", Range(0, 1)) = 1
        _TrafficTex("Traffic Texture", 2D) = "black" {}
        _OverlayFrontTex("Overlay Front Texture", 2D) = "black" {}
        _OverlayFrontAlpha("Overlay Front Alpha", Range(0, 1)) = 1
        
        _OverlayTex("Overlay Texture", 2D) = "black" {}
        _OverlayColor("Overlay Color", Color) = (1,1,1,1)
        _OverlayAlpha("Overlay Alpha", Range(0, 1)) = 1
        _OverlayTL("Overlay Top Left", Vector) = (0, 0, 0, 0)
        _OverlayBR("Overlay Bottom Right", Vector) = (1, 1, 0, 0)
    }

    SubShader 
    {
        Tags {"Queue"="AlphaTest-300" "IgnoreProjector"="True" "RenderType"="TransparentCutout"}
        LOD 200

        CGPROGRAM
        #pragma surface surf Lambert alphatest:_Cutoff 

        sampler2D _MainTex;
        sampler2D _OverlayBackTex;
        half _OverlayBackAlpha;
        sampler2D _TrafficTex;
        sampler2D _OverlayFrontTex;
        half _OverlayFrontAlpha;
        fixed4 _Color;

        sampler2D _OverlayTex;
        fixed4 _OverlayColor;
        half _OverlayAlpha;
        float4 _OverlayTL;
        float4 _OverlayBR;

        struct Input
        {
            float2 uv_MainTex;
            float2 uv_OverlayBackTex;
            float2 uv_TrafficTex;
            float2 uv_OverlayFrontTex;
            float3 worldPos;
        };

        void surf(Input IN, inout SurfaceOutput o)
        {
            fixed4 c = tex2D(_MainTex, IN.uv_MainTex);

            fixed4 t = tex2D(_OverlayBackTex, IN.uv_OverlayBackTex);
            fixed3 ct = lerp(c.rgb, t.rgb, t.a * _OverlayBackAlpha);

            t = tex2D(_TrafficTex, IN.uv_TrafficTex);
            ct = lerp(ct, t.rgb, t.a);

            t = tex2D(_OverlayFrontTex, IN.uv_OverlayFrontTex);
            ct = lerp(ct, t.rgb, t.a * _OverlayFrontAlpha);

            ct = ct * _Color;
            
            o.Albedo = ct;
            o.Alpha = c.a * _Color.a;

            float3 wp = IN.worldPos;
            
            float uvx = (wp.x - _OverlayTL.x) / (_OverlayBR.x - _OverlayTL.x);
            float uvy = (wp.z - _OverlayBR.z) / (_OverlayTL.z - _OverlayBR.z);

            if (uvx >= 0 && uvx <= 1 && uvy >= 0 && uvy <= 1)
            {
                t = tex2D(_OverlayTex, float2(uvx, uvy));
                fixed3 ct2 = lerp(t.rgb, _OverlayColor.rgb, _OverlayColor.a);
                o.Albedo = lerp(ct, ct2, t.a * _OverlayAlpha);
            }
        }
        ENDCG
    }

    Fallback "Transparent/Cutout/Diffuse"
}