Shader "Unlit/LiquidStar"
{
    Properties
    {
        _Speed("Flow Speed", Range(0.01, 5.0)) = 0.8
        _Scale("Surface Scale", Range(0.5, 20.0)) = 3.0
        _BaseColor("Base Color", Color) = (1.0, 0.1, 0.0, 1.0)
        _HotColor("Hot Spot Color", Color) = (1.0, 0.9, 0.2, 1.0)
        _SpotColor("Dark Color", Color) = (0.3, 0.0, 0.0, 1.0)
        _GlowIntensity("Glow Intensity", Range(1.0, 20.0)) = 6.0
        _Turbulence("Turbulence", Range(0.0, 3.0)) = 1.2
        _EdgeSoftness("Edge Softness", Range(0.01, 0.3)) = 0.08
        _CoronaSize("Corona Size", Range(0.0, 0.4)) = 0.15
        _CoronaIntensity("Corona Intensity", Range(0.0, 10.0)) = 3.0
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" "Queue"="Geometry" }
        LOD 100
        ZWrite On
        Cull Off

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

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

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            float _Speed;
            float _Scale;
            float4 _BaseColor;
            float4 _HotColor;
            float4 _SpotColor;
            float _GlowIntensity;
            float _Turbulence;
            float _EdgeSoftness;
            float _CoronaSize;
            float _CoronaIntensity;

            // 3D simplex-style noise
            float3 mod289(float3 x) { return x - floor(x * (1.0 / 289.0)) * 289.0; }
            float4 mod289(float4 x) { return x - floor(x * (1.0 / 289.0)) * 289.0; }
            float4 permute(float4 x) { return mod289(((x * 34.0) + 10.0) * x); }
            float4 taylorInvSqrt(float4 r) { return 1.79284291400159 - 0.85373472095314 * r; }

            float snoise(float3 v)
            {
                const float2 C = float2(1.0 / 6.0, 1.0 / 3.0);
                const float4 D = float4(0.0, 0.5, 1.0, 2.0);

                float3 i = floor(v + dot(v, C.yyy));
                float3 x0 = v - i + dot(i, C.xxx);

                float3 g = step(x0.yzx, x0.xyz);
                float3 l = 1.0 - g;
                float3 i1 = min(g.xyz, l.zxy);
                float3 i2 = max(g.xyz, l.zxy);

                float3 x1 = x0 - i1 + C.xxx;
                float3 x2 = x0 - i2 + C.yyy;
                float3 x3 = x0 - D.yyy;

                i = mod289(i);
                float4 p = permute(permute(permute(
                    i.z + float4(0.0, i1.z, i2.z, 1.0))
                    + i.y + float4(0.0, i1.y, i2.y, 1.0))
                    + i.x + float4(0.0, i1.x, i2.x, 1.0));

                float n_ = 0.142857142857;
                float3 ns = n_ * D.wyz - D.xzx;

                float4 j = p - 49.0 * floor(p * ns.z * ns.z);

                float4 x_ = floor(j * ns.z);
                float4 y_ = floor(j - 7.0 * x_);

                float4 x = x_ * ns.x + ns.yyyy;
                float4 y = y_ * ns.x + ns.yyyy;
                float4 h = 1.0 - abs(x) - abs(y);

                float4 b0 = float4(x.xy, y.xy);
                float4 b1 = float4(x.zw, y.zw);

                float4 s0 = floor(b0) * 2.0 + 1.0;
                float4 s1 = floor(b1) * 2.0 + 1.0;
                float4 sh = -step(h, float4(0, 0, 0, 0));

                float4 a0 = b0.xzyw + s0.xzyw * sh.xxyy;
                float4 a1 = b1.xzyw + s1.xzyw * sh.zzww;

                float3 p0 = float3(a0.xy, h.x);
                float3 p1 = float3(a0.zw, h.y);
                float3 p2 = float3(a1.xy, h.z);
                float3 p3 = float3(a1.zw, h.w);

                float4 norm = taylorInvSqrt(float4(dot(p0,p0), dot(p1,p1), dot(p2,p2), dot(p3,p3)));
                p0 *= norm.x;
                p1 *= norm.y;
                p2 *= norm.z;
                p3 *= norm.w;

                float4 m = max(0.6 - float4(dot(x0,x0), dot(x1,x1), dot(x2,x2), dot(x3,x3)), 0.0);
                m = m * m;
                return 42.0 * dot(m * m, float4(dot(p0,x0), dot(p1,x1), dot(p2,x2), dot(p3,x3)));
            }

            // Fractal brownian motion
            float fbm(float3 p, int octaves)
            {
                float value = 0.0;
                float amplitude = 0.5;
                float frequency = 1.0;
                for (int i = 0; i < octaves; i++)
                {
                    value += amplitude * snoise(p * frequency);
                    amplitude *= 0.5;
                    frequency *= 2.0;
                }
                return value;
            }

            v2f vert(appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }

            float4 frag(v2f i) : SV_Target
            {
                // Remap UV to centered [-1, 1] range
                float2 centeredUV = i.uv * 2.0 - 1.0;

                // Shrink the star so disk + corona fits inside the quad
                float starRadius = 1.0 / (1.0 + _CoronaSize);
                float dist = length(centeredUV) / starRadius;

                // Discard outside the circle + corona
                if (dist > 1.0 + _CoronaSize) discard;

                float time = _Time.y * _Speed;

                // Use UV-based 3D coordinate for noise (flat plane, no sphere artifacts)
                float3 p = float3(centeredUV * _Scale, time * 0.02);

                // Liquid flow - domain warping (2 octaves for island edges)
                float3 q = float3(
                    fbm(p + float3(0.0, 0.0, time * 0.06), 2),
                    fbm(p + float3(5.2, 1.3, time * 0.05), 2),
                    fbm(p + float3(1.7, 9.2, time * 0.07), 2)
                );

                // Inner layer - single pass smooth fill
                float3 r = float3(
                    snoise(p + _Turbulence * q + float3(1.7, 9.2, time * 0.03)),
                    snoise(p + _Turbulence * q + float3(8.3, 2.8, time * 0.04)),
                    snoise(p + _Turbulence * q + float3(3.1, 6.5, time * 0.02))
                );

                float liquidPattern = snoise(p + _Turbulence * r);

                // Convection cells - granulation pattern
                float granulation = snoise(float3(centeredUV * _Scale * 3.0, time * 0.08));
                granulation = granulation * 0.5 + 0.5;

                // Blend colors - use granulation heavily for contrast
                float heatMap = liquidPattern * 0.5 + 0.5;
                heatMap = saturate(heatMap * granulation);
                heatMap = pow(heatMap, 0.7);

                // Base liquid surface color
                float3 col = lerp(_SpotColor.rgb, _BaseColor.rgb, heatMap);
                col = lerp(col, _HotColor.rgb, pow(heatMap, 2.5));

                // Limb darkening - darken edges of the star disk
                float limbDarken = 1.0 - pow(dist, 2.0);
                col *= max(limbDarken, 0.3);

                // HDR glow intensity
                col *= _GlowIntensity;

                // Outside the star disk: corona fading to black
                if (dist > 1.0)
                {
                    float coronaDist = (dist - 1.0) / _CoronaSize;
                    float coronaFade = (1.0 - coronaDist) * (1.0 - coronaDist);
                    col = lerp(_BaseColor.rgb, _HotColor.rgb, 0.7) * _CoronaIntensity * coronaFade;
                }
                else if (dist > 1.0 - _EdgeSoftness)
                {
                    // Soft edge of star disk
                    float edgeFade = smoothstep(1.0, 1.0 - _EdgeSoftness, dist);
                    col = lerp(float3(0, 0, 0), col, edgeFade);
                }

                return float4(col, 1.0);
            }
            ENDCG
        }
    }
}