/*{
  "DESCRIPTION": "Folded jewel fractal — emerald/sapphire/amethyst facets with gold ignition, rotating as a seamless 8s loop on a void-black field.",
  "INPUTS": [
    { "NAME": "hueShift", "TYPE": "float", "DEFAULT": 0.0, "MIN": 0.0, "MAX": 1.0 },
    { "NAME": "glowAmt",  "TYPE": "float", "DEFAULT": 1.0, "MIN": 0.0, "MAX": 2.0 }
  ]
}*/

#define PI 3.14159265359
#define PERIOD 8.0

mat2 rot(float a){ float c = cos(a), s = sin(a); return mat2(c, -s, s, c); }

float gTrap;
float gFold;

float de(vec3 p){
  vec3 p0 = p;
  float dr = 1.0;
  float trap = 1e9;
  float fold = 0.0;
  for (int i = 0; i < 9; i++){
    p = clamp(p, -1.0, 1.0) * 2.0 - p;          // box fold
    float r2 = dot(p, p);
    if (r2 < 0.25){ p *= 4.0; dr *= 4.0; }      // sphere fold
    else if (r2 < 1.0){ p /= r2; dr /= r2; }
    p = p * (-1.75) + p0;
    dr = dr * 1.75 + 1.0;
    if (r2 < trap){ trap = r2; fold = float(i); }
  }
  gTrap = trap;
  gFold = fold;
  return (length(p) - 2.0) / abs(dr);
}

float map(vec3 p){
  float ph = fract(TIME / PERIOD);
  float th = 2.0 * PI * ph;
  p.xz *= rot(th);          // one full turn per loop — exact
  p.xy *= rot(0.6);         // fixed tilt
  return de(p * 3.9) / 3.9;
}

vec3 jewel(float t){
  // 4-stop jewel gradient: sapphire -> emerald -> amethyst -> gold
  t = fract(t);
  vec3 sap = vec3(0.05, 0.18, 0.75);
  vec3 eme = vec3(0.04, 0.75, 0.38);
  vec3 ame = vec3(0.55, 0.15, 0.85);
  vec3 gld = vec3(1.00, 0.72, 0.15);
  float k = t * 4.0;
  if (k < 1.0) return mix(sap, eme, k);
  if (k < 2.0) return mix(eme, ame, k - 1.0);
  if (k < 3.0) return mix(ame, gld, k - 2.0);
  return mix(gld, sap, k - 3.0);
}

void main(){
  vec2 uv = (gl_FragCoord.xy - 0.5 * RENDERSIZE.xy) / RENDERSIZE.y;
  vec3 ro = vec3(0.0, 0.0, 3.4);
  vec3 rd = normalize(vec3(uv, -1.45));

  float t = 0.0;
  float hit = -1.0;
  float nearGlow = 0.0;
  for (int i = 0; i < 100; i++){
    vec3 pos = ro + rd * t;
    float d = map(pos);
    nearGlow += exp(-d * 22.0) * 0.012;
    if (d < 0.0006 * t){ hit = t; break; }
    t += d * 0.6;
    if (t > 12.0) break;
  }

  vec3 void_col = vec3(0.008, 0.016, 0.04);   // #02040a-ish
  vec3 col = void_col;

  if (hit > 0.0){
    vec3 p = ro + rd * hit;
    float trap = gTrap;
    float fold = gFold;
    // 4-tap tetrahedron normal
    vec2 e = vec2(0.0012, -0.0012);
    vec3 n = 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));

    // hue from fold depth + orbit trap (decoupled from density)
    float hueArg = 0.52 + fold * 0.085 + trap * 0.6 + hueShift;
    vec3 base = jewel(hueArg);

    vec3 L = normalize(vec3(0.6, 0.8, 0.5));
    float dif = max(dot(n, L), 0.0);
    float rim = pow(1.0 - max(dot(n, -rd), 0.0), 3.0);
    float spec = pow(max(dot(reflect(-L, n), -rd), 0.0), 32.0);

    float emis = smoothstep(0.15, 0.0, trap);           // only the tightest fold cores ignite
    col = base * (0.10 + 0.75 * dif);
    col += base * emis * 3.0 * glowAmt;                 // jewel-emissive core
    col += vec3(1.0, 0.85, 0.55) * spec * 0.6;          // gold specular
    col += base * rim * 0.35;
    col *= exp(-0.22 * hit);                             // depth fog to void
  }

  col += jewel(0.05 + hueShift) * nearGlow * glowAmt * 0.35;  // halo
  col = col / (1.0 + 0.35 * col);                             // soft-knee, keeps darks dark
  gl_FragColor = vec4(col, 1.0);
}