Sprite 2D Shadow Shader

Hello,
maybe there are thousands solutions but i really can't find any. So i have this SOLID COLOR shader, that i am using right now to make 2D Shadows for my sprites. Example below. Now i want it to have transparency but i don't know how. Could someone give me a hint? To be clear. I want my sprite to be full black for example with transparency of 0.5. There are transparency shaders but they don't make the full sprite black at first, they just make everything transparent, but thats not how shadows work unfortunately...

Code (CSharp):

1. Shader "Sprites/SolidCol"
2. {
3.     Properties
4.     {
5.         [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
6.         _Color ("Tint", Color) = (1,1,1,1)
7.         [MaterialToggle] PixelSnap ("Pixel snap", Float) = 0
8.     }
9.  
10.     SubShader
11.     {
12.         Tags
13.         {
14.             "Queue"="Transparent"
15.             "IgnoreProjector"="True"
16.             "RenderType"="Transparent"
17.             "PreviewType"="Plane"
18.             "CanUseSpriteAtlas"="True"
19.         }
20.  
21.         Cull Off
22.         Lighting Off
23.         ZWrite Off
24.         Fog { Mode Off }
25.         Blend One OneMinusSrcAlpha
26.  
27.         Pass
28.         {
29.         CGPROGRAM
30.             #pragma vertex vert
31.             #pragma fragment frag
32.             #pragma multi_compile DUMMY PIXELSNAP_ON
33.             #include "UnityCG.cginc"
34.  
35.             struct appdata_t
36.             {
37.                 float4 vertex   : POSITION;
38.                 float4 color    : COLOR;
39.                 float2 texcoord : TEXCOORD0;
40.             };
41.  
42.             struct v2f
43.             {
44.                 float4 vertex   : SV_POSITION;
45.                 fixed4 color    : COLOR;
46.                 half2 texcoord  : TEXCOORD0;
47.             };
48.  
49.             fixed4 _Color;
50.  
51.             v2f vert(appdata_t IN)
52.             {
53.                 v2f OUT;
54.                 OUT.vertex = UnityObjectToClipPos(IN.vertex);
55.                 OUT.texcoord = IN.texcoord;
56.                 OUT.color = IN.color * _Color;
57.                 #ifdef PIXELSNAP_ON
58.                 OUT.vertex = UnityPixelSnap (OUT.vertex);
59.                 #endif
60.  
61.                 return OUT;
62.             }
63.  
64.             sampler2D _MainTex;
65.  
66.             fixed4 frag(v2f IN) : SV_Target
67.             {
68.                 fixed4 c = tex2D(_MainTex, IN.texcoord);
69.                 c.rgb = IN.color * c.a;
70.                 return c;
71.             }
72.         ENDCG
73.         }
74.     }
75. }