ToonLitシェーダでテクスチャの透過がされない

Unity標準のToon/Litシェーダを改変したものを使っているのですが
テクスチャに使っているpng画像のアルファ値が反映されなくなってしまいました。

どうしたら良いでしょうか。

Shader "ToonLitRemake" {
	Properties {
		_Color ("Main Color", Color) = (0.5,0.5,0.5,1)
		_MainTex ("Base (RGB)", 2D) = "white" {}
		_Ramp ("Toon Ramp (RGB)", 2D) = "gray" {} 
	}

	SubShader {
		Tags { "IgnoreProjector"="True"  "RenderType" = "Transparent" }
		Blend SrcAlpha OneMinusSrcAlpha
		LOD 200
	Pass
        {
            ZWrite ON
            ColorMask 0
			
        }

	Pass{
            Name "BASE"
            //Cull Off
			
	}

		CGPROGRAM
		#pragma surface surf ToonRamp

		sampler2D _Ramp;

		// custom lighting function that uses a texture ramp based
		// on angle between light direction and normal
		#pragma lighting ToonRamp exclude_path:prepass
		inline half4 LightingToonRamp (SurfaceOutput s, half3 lightDir, half atten)
		{
			#ifndef USING_DIRECTIONAL_LIGHT
			lightDir = normalize(lightDir);
			#endif
			
			half d = dot (s.Normal, lightDir)*0.5 + 0.5;
			half3 ramp = tex2D (_Ramp, float2(d,d)).rgb;
			
			half4 c;
			c.rgb = s.Albedo * _LightColor0.rgb * ramp * (atten * 2);
			c.a = 0;
			return c;
		}


		sampler2D _MainTex;
		float4 _Color;

		struct Input {
			float2 uv_MainTex : TEXCOORD0;
		};

		void surf (Input IN, inout SurfaceOutput o) {
			half4 c = tex2D(_MainTex, IN.uv_MainTex) * _Color;
			o.Albedo = c.rgb;
			o.Alpha = c.a;
		}
		ENDCG
	

	} 

	Fallback "Diffuse"
}

【追記】
閲覧してくださった方ありがとうございます。
こちらを参考に自分で作ってみました。リンク内容
・PNGテクスチャのアルファ有効
・前後関係の正しい半透明処理有効

Shader "ToonLitRemake" {

         Properties {
             _Color ("Main Color", Color) = (0.5,0.5,0.5,1)
		_MainTex ("Alpha Blended (RGBA) ", 2D) = "white" {}
             _Ramp ("Toon Ramp (RGB)", 2D) = "gray" {} 
         }
     
         SubShader {
             Tags {"Queue"="Transparent" "RenderType"="Transparent"}
             Blend SrcAlpha OneMinusSrcAlpha
             LOD 200
             
		Pass{
  		  ZWrite ON
  		  ColorMask 0
		}



     CGPROGRAM
     #pragma surface surf ToonRamp  alpha:fade
     
     sampler2D _Ramp;
     
     // custom lighting function that uses a texture ramp based
     // on angle between light direction and normal
     #pragma lighting ToonRamp exclude_path:prepass
     inline half4 LightingToonRamp (SurfaceOutput s, half3 lightDir, half atten)
     {
         #ifndef USING_DIRECTIONAL_LIGHT
         lightDir = normalize(lightDir);
         #endif
         
         half d = dot (s.Normal, lightDir)*0.5 + 0.5;
         half3 ramp = tex2D (_Ramp, float2(d,d)).rgb;
         
         half4 c;
         c.rgb = s.Albedo * _LightColor0.rgb * ramp * (atten * 2);
         c.a = s.Alpha;
         return c;
     }
     
     
     sampler2D _MainTex;
     float4 _Color;
     
     struct Input {
         float2 uv_MainTex : TEXCOORD0;
     };
     
     void surf (Input IN, inout SurfaceOutput o) {
         half4 c = tex2D(_MainTex, IN.uv_MainTex) * _Color;
         o.Albedo = c.rgb;
         o.Alpha = c.a;
     }
     ENDCG
     
         } 
     
         Fallback "Diffuse"
     }