Shader "Unlit/Wavy2"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Len ("Len", float) = 1
        _Alpha ("Alpha", float) = 1.0
    }
    SubShader
    {
        Tags { "Queue"="Transparent" } 
        
        LOD 100
        
        Cull Off
        
        Pass
        {
            Blend SrcAlpha OneMinusSrcAlpha  
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // #pragma cull off
            // make fog work
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float _Len;
            float _Alpha;

            v2f vert (appdata v)
            {
                v2f o;
                float4 vout = v.vertex;
                float angle = v.vertex.x * UNITY_PI * 2 * _Len;
                vout.x = sin(angle);
                vout.y = 1 - cos(angle);
                o.vertex = UnityObjectToClipPos(vout);
                o.uv = v.uv;
                UNITY_TRANSFER_FOG(o, o.vertex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);
                col.a *= _Alpha; // apply transparency

                float speed = 2;
                float width = 0.01;
                float currentTime = _Time.y * speed;
                float lightPosition = fmod(currentTime, 1.0);
                float distanceToLight = abs(i.uv.x - lightPosition);

                if (distanceToLight < width)
                {
                    float intensity = 0.5 * (1.5 - (distanceToLight / width));
                    col *= intensity;
                }
                else
                {
                    col *= 0.2;
                }

                return col;
            }
            ENDCG
        }
    }
}