Shader "Custom/VertexLit"
{
  Properties
  {
    _Dark ("Dark", Color) = (0, 0, 0, 1)
    _Mid ("Mid", Color) = (1, 1, 1, 1)
  }
  SubShader
  {
    Tags { "RenderType"="Opaque" }

    Pass
    {
      CGPROGRAM
      #pragma vertex vert
      #pragma fragment frag

      #include "UnityCG.cginc"

      struct appdata
      {
        float4 vertex : POSITION;
        float3 normal : NORMAL;
        fixed4 color : COLOR;
      };

      struct v2f
      {
        float4 vertex : SV_POSITION;
        float3 normal : TEXCOORD;
        fixed4 color : COLOR;
      };

      fixed4 _Dark;
      fixed4 _Mid;

      v2f vert (appdata v)
      {
        v2f o;
        o.vertex = UnityObjectToClipPos(v.vertex);
        o.normal = UnityObjectToWorldNormal(v.normal);
        float t = clamp(dot(normalize(float3(0.3, 0.6, -0.2)), o.normal), 0, 1);
        o.color = lerp(_Dark, _Mid, t);

        return o;
      }

      fixed4 frag (v2f i) : SV_Target
      {
        return i.color;
      }
      ENDCG
    }
  }
}