/*{
  "DESCRIPTION": "Chrome Dreams: blobs of liquid mercury merge and split in a dark neon studio. Pure reflection plus oil-slick thin-film iridescence — no emission, all reflected light — so the metal smears the colored studio lights across its writhing surface. Blobs orbit on integer cycles for a seamless 16s loop.",
  "CREDIT": "glslop agent (Claude)",
  "CATEGORIES": ["metaball", "chrome", "reflection", "iridescent", "liquid"],
  "INPUTS": [
    { "NAME": "speed",  "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.0, "MAX": 3.0 },
    { "NAME": "irid",   "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.0, "MAX": 2.0 },
    { "NAME": "hue",    "TYPE": "float", "DEFAULT": 0.0,  "MIN": 0.0, "MAX": 1.0 },
    { "NAME": "merge",  "TYPE": "float", "DEFAULT": 0.45, "MIN": 0.2, "MAX": 0.9 },
    { "NAME": "zoom",   "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.6, "MAX": 1.8 }
  ]
}*/

#define PI  3.14159265359
#define TAU 6.28318530718
#define NB 6

const float PERIOD = 16.0;

mat2 rot(float a){ float c = cos(a), s = sin(a); return mat2(c, -s, s, c); }
vec3 pal(float t){ return 0.5 + 0.5 * cos(TAU * (t + vec3(0.0, 0.33, 0.66))); }

float gTh, gMerge;

float smin(float a, float b, float k){
  float h = clamp(0.5 + 0.5 * (b - a) / k, 0.0, 1.0);
  return mix(b, a, h) - k * h * (1.0 - h);
}

float map(vec3 p){
  float d = length(p) - 0.55;                 // central core blob
  for (int i = 0; i < NB; i++){
    float fi = float(i);
    float a  = gTh * (1.0 + mod(fi, 2.0)) + fi * (TAU / float(NB));
    float rr = 0.72 + 0.20 * sin(gTh * 2.0 + fi);
    vec3 c = rr * vec3(cos(a) * cos(0.7 * fi), sin(a), cos(a) * sin(0.7 * fi));
    d = smin(d, length(p - c) - (0.30 + 0.08 * sin(gTh + fi)), gMerge);
  }
  return d;
}

vec3 calcNormal(vec3 p){
  vec2 e = vec2(1.0, -1.0) * 0.001;
  return normalize(
      e.xyy * map(p + e.xyy) + e.yyx * map(p + e.yyx)
    + e.yxy * map(p + e.yxy) + e.xxx * map(p + e.xxx));
}

// dark studio with a few coloured neon strip-lights for the chrome to reflect
vec3 env(vec3 d, float hue){
  vec3 c = mix(vec3(0.015, 0.02, 0.04), vec3(0.05, 0.03, 0.08), d.y * 0.5 + 0.5);
  float az = atan(d.z, d.x);
  // three broad colour bars at different elevations
  c += pal(hue + 0.00) * smoothstep(0.25, 0.0, abs(d.y - 0.55)) * smoothstep(0.6, 1.0, sin(az * 2.0) * 0.5 + 0.5) * 1.4;
  c += pal(hue + 0.45) * smoothstep(0.20, 0.0, abs(d.y + 0.10)) * 1.0;
  c += pal(hue + 0.75) * smoothstep(0.18, 0.0, abs(d.y + 0.6))  * smoothstep(0.5, 1.0, cos(az * 3.0) * 0.5 + 0.5) * 1.2;
  // a bright key highlight
  c += vec3(1.0) * pow(max(dot(d, normalize(vec3(0.5, 0.7, 0.3))), 0.0), 40.0) * 2.0;
  return c;
}

void main(){
  vec2 uv = (gl_FragCoord.xy - 0.5 * RENDERSIZE.xy) / RENDERSIZE.y;
  float ph = fract(TIME * speed / PERIOD);
  gTh = TAU * ph;
  gMerge = merge;

  vec3 ro = vec3(0.0, 0.0, 4.1 / zoom);
  vec3 ta = vec3(0.0);
  vec3 ww = normalize(ta - ro);
  vec3 uu = normalize(cross(vec3(0.0, 1.0, 0.0), ww));
  vec3 vv = cross(ww, uu);
  vec3 rd = normalize(uv.x * uu + uv.y * vv + 1.6 * ww);

  vec3 col = env(rd, hue);                      // background = the studio itself
  float t = 0.0;
  bool hit = false;
  for (int s = 0; s < 110; s++){
    vec3 p = ro + rd * t;
    float d = map(p);
    if (d < 0.0007 * t){ hit = true; break; }
    t += d * 0.85;
    if (t > 9.0) break;
  }

  if (hit){
    vec3 p = ro + rd * t;
    vec3 nor = calcNormal(p);
    float fres = pow(1.0 - max(dot(nor, -rd), 0.0), 5.0);

    vec3 refl = reflect(rd, nor);
    vec3 rc = env(refl, hue);                   // mirror reflection of the studio
    // thin-film iridescence: a colour wash keyed to angle + Fresnel
    vec3 film = pal(hue + 0.5 + 2.2 * fres + 0.3 * nor.y);
    vec3 metal = mix(rc, rc * film * 1.6, irid * 0.6);
    metal += film * fres * irid * 0.8;
    col = mix(metal, vec3(1.0), fres * 0.15);   // edge glare
  }

  col = col / (1.0 + col);
  col = pow(col, vec3(0.85));
  col *= 1.0 - 0.16 * dot(uv, uv);

  gl_FragColor = vec4(col, 1.0);
}