Shader "Skybox/PsychedelicSkyboxURP_SineFlow"
{
    Properties
    {
        _BaseColor ("Base Color", Color) = (0.05, 0.05, 0.08, 1)
        _AccentColor ("Accent Color", Color) = (0.2, 0.8, 1.0, 1)
        _SecondaryColor ("Secondary Color", Color) = (1.0, 0.6, 0.2, 1)
        _Intensity ("Emission Intensity", Range(0, 10)) = 2.5
        _Speed ("Animation Speed", Range(0.1, 5)) = 1.0
        _WarpStrength ("Warp Strength", Range(0.0, 2.0)) = 0.6
    }

    SubShader
    {
        Tags { "RenderType"="Background" "Queue"="Background" "PreviewType"="Skybox" }
        Cull Off ZWrite Off ZTest Always

        Pass
        {
            Name "SkyboxPass"
            Tags { "LightMode"="UniversalForward" }

            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            // === Properties ===
            float4 _BaseColor;
            float4 _AccentColor;
            float4 _SecondaryColor;
            float _Intensity;
            float _Speed;
            float _WarpStrength;

            struct Attributes
            {
                float4 positionOS : POSITION;
            };

            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                float3 viewDirWS  : TEXCOORD0;
            };

            Varyings vert(Attributes v)
            {
                Varyings o;
                o.positionCS = TransformObjectToHClip(v.positionOS.xyz);
                o.viewDirWS = GetSkyboxViewDirWS(v.positionOS.xyz);
                return o;
            }

            half4 frag(Varyings i) : SV_Target
            {
                // Convert 3D direction to a 2D UV projection
                float3 dir = normalize(i.viewDirWS);
                float2 uv = dir.xy / max(1e-3, (1.0 + dir.z)); // spherical projection

                float time = _Time.y * _Speed;

                // --- Warping loop (GLSL style port) ---
                float2 warped = uv;
                [unroll(9)]
                for (float j = 1.0; j < 10.0; j++)
                {
                    warped.x += _WarpStrength / j * cos(j * 2.5 * warped.y + time);
                    warped.y += _WarpStrength / j * cos(j * 1.5 * warped.x + time);
                }

                float glow = 0.1 / abs(sin(time - warped.y - warped.x));
                glow = saturate(glow * 5.0);

                float3 col = lerp(_BaseColor.rgb, _AccentColor.rgb, glow);
                col = lerp(col, _SecondaryColor.rgb, pow(glow, 3.0));

                return half4(col * _Intensity, 1.0);
            }
            ENDHLSL
        }
    }

    FallBack Off
}