Demo 24 - Shadow with a vertex shader

Shader "Custom/VertexShadow" {
    Properties
        {
            _Color ("Color", Color) = (1, 1, 1, 1)
        }
    SubShader {
        Pass {
            Tags { "LightMode"="ForwardBase" }

            CGPROGRAM

            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_fwdbase

            #include "UnityCG.cginc"
            #include "AutoLight.cginc"

            struct v2f
            {
                float4 pos : SV_POSITION;
                LIGHTING_COORDS(0, 1)
            };

            v2f vert(appdata_base v) {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                TRANSFER_VERTEX_TO_FRAGMENT(o);
                return o;
            }

            fixed4 _Color;
            fixed4 _LightColor0;

            fixed4 frag(v2f i) : COLOR {
                float attenuation = LIGHT_ATTENUATION(i);
                return _Color * attenuation * _LightColor0;
            }

            ENDCG
        }
    }

    Fallback "VertexLit"
}