/*{
  "DESCRIPTION": "Laser Mandelbox: a box-fold/sphere-fold KIFS field that slowly tumbles and resolves into glowing cathedral shapes, raymarched in near-black with bold hot laser lines etched along its folds. Electric neon, real-time, seamless 16s loop.",
  "CREDIT": "glslop agent (Claude)",
  "CATEGORIES": ["fractal", "raymarch", "neon", "mandelbox"],
  "INPUTS": [
    { "NAME": "speed",     "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.0, "MAX": 3.0 },
    { "NAME": "glow",      "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.3, "MAX": 3.0 },
    { "NAME": "hue",       "TYPE": "float", "DEFAULT": 0.0,  "MIN": 0.0, "MAX": 1.0 },
    { "NAME": "boxScale",  "TYPE": "float", "DEFAULT": 2.05, "MIN": -3.0,"MAX": 3.0 },
    { "NAME": "tumble",    "TYPE": "float", "DEFAULT": 0.5,  "MIN": 0.0, "MAX": 1.5 },
    { "NAME": "zoom",      "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.5, "MAX": 2.0 },
    { "NAME": "iterCount", "TYPE": "long",  "DEFAULT": 8,    "MIN": 4,   "MAX": 14 }
  ]
}*/

#define PI  3.14159265359
#define TAU 6.28318530718

const float PERIOD = 16.0;   // seconds per seamless loop
const int   MAXI   = 14;     // hard cap on KIFS iterations (>= iterCount MAX)
const int   STEPS  = 100;    // raymarch steps (kept low for real-time)

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

// electric neon palette (cyan / magenta / violet, not a flat rainbow)
vec3 pal(float t){
  return 0.5 + 0.5 * cos(TAU * (t + vec3(0.55, 0.40, 0.18)));
}

// Mandelbox DE (Tglad box-fold + sphere-fold). Conservative -> clean march.
// No sqrt in the loop (squared traps) for speed.
// trap -> body color ; lineT2 -> squared dist to nearest axis (laser lines).
float map(vec3 p, mat2 R1, mat2 R2, out float trap, out float lineT2){
  float fs = 3.8;                   // shrink the fractal so it reads as an object
  vec3 c = p * fs;
  c.xz = R1 * c.xz;                 // rigid tumble of the whole fractal
  c.xy = R2 * c.xy;
  vec3 z = c;
  float dr = 1.0;
  trap = 1.0e9; lineT2 = 1.0e9;
  for (int i = 0; i < MAXI; i++){
    if (i >= iterCount) break;
    z = clamp(z, -1.0, 1.0) * 2.0 - z;            // box fold
    float r2 = dot(z, z);                          // sphere fold
    if (r2 < 0.25){ z *= 4.0; dr *= 4.0; }         // 1/minR2, minR2 = 0.25
    else if (r2 < 1.0){ float s = 1.0 / r2; z *= s; dr *= s; }
    z = z * boxScale + c;
    dr = dr * abs(boxScale) + 1.0;
    trap   = min(trap, dot(z, z));
    lineT2 = min(lineT2, min(min(dot(z.xy, z.xy), dot(z.yz, z.yz)), dot(z.xz, z.xz)));
  }
  return length(z) / abs(dr) / fs;        // undo the input scale
}

void main(){
  vec2 uv = (gl_FragCoord.xy - 0.5 * RENDERSIZE.xy) / RENDERSIZE.y;

  // seamless loop: every angle is sin/cos of an integer multiple of th.
  // Gentle, eased motion so the fractal settles into readable shapes.
  float ph = fract(TIME * speed / PERIOD);
  float th = TAU * ph;
  mat2 R1 = rot(th);                                   // one slow tumble / loop
  mat2 R2 = rot(0.4 + 0.18 * tumble * sin(th));        // gentle breathing fold

  // calm camera: mostly parked, slight eased drift
  float camDist = 8.0 * zoom;
  float az = 0.18 * sin(th);
  float el = 0.32 + 0.10 * sin(th);
  vec3 ro = camDist * vec3(sin(az) * cos(el), sin(el), cos(az) * cos(el));
  vec3 ta = vec3(0.0);
  vec3 fwd = normalize(ta - ro);
  vec3 rgt = normalize(cross(vec3(0.0, 1.0, 0.0), fwd));
  vec3 upv = cross(fwd, rgt);
  vec3 rd  = normalize(uv.x * rgt + uv.y * upv + 1.6 * fwd);

  // ---- surface raymarch ----
  float t = 0.05;
  float tcap = camDist + 8.0;
  float trap = 1.0e9, lineT2 = 1.0e9, trapHit = 1.0e9, lineHit2 = 1.0e9, te = 0.0;
  bool hit = false;
  for (int i = 0; i < STEPS; i++){
    vec3 p = ro + rd * t;
    float tr, l2;
    float d = map(p, R1, R2, tr, l2);
    if (d < 0.0005 * t){ hit = true; trapHit = tr; lineHit2 = l2; te = t; break; }
    t += d * 0.85;
    if (t > tcap) break;
  }

  vec3 col = vec3(0.0);

  if (hit){
    vec3 p = ro + rd * te;
    // 4-tap tetrahedron normal (cheaper than 6-tap central difference)
    vec2 k = vec2(1.0, -1.0);
    float e = 0.0013, tr, l2;
    vec3 n = normalize(
      k.xyy * map(p + k.xyy * e, R1, R2, tr, l2) +
      k.yyx * map(p + k.yyx * e, R1, R2, tr, l2) +
      k.yxy * map(p + k.yxy * e, R1, R2, tr, l2) +
      k.xxx * map(p + k.xxx * e, R1, R2, tr, l2));

    vec3 body = pal(hue + 0.55 * sqrt(trapHit) + 0.14 * te);   // richer colour spread
    vec3 lig  = normalize(vec3(0.4, 0.8, 0.45));
    float dif = max(dot(n, lig), 0.0);
    float fres = pow(1.0 - max(dot(n, -rd), 0.0), 2.3);

    // bold hot laser lines along the folds (lineHit2 is already squared)
    float laser = 1.0 / (1.0 + 110.0 * lineHit2);
    laser = pow(laser, 1.6);
    vec3 laserCol = mix(vec3(0.9, 0.97, 1.0), body + 0.4, 0.3);

    col += body * 0.025;                   // near-black body
    col += body * dif * 0.07;              // faint shading
    col += body * fres * 2.1 * glow;       // rim glow -> pops the portal rings
    col += laserCol * laser * 8.0 * glow;  // the LASER lines dominate
    // depth fog -> far structure fades into black for clean 3D depth
    col *= exp(-0.20 * max(te - camDist + 3.5, 0.0));
  }

  // tone map: hot cores blow to white, halos stay saturated
  col *= 1.08;
  col = col / (1.0 + col);
  col = pow(col, vec3(0.76));
  col *= 1.0 - 0.24 * dot(uv, uv);         // vignette

  gl_FragColor = vec4(col, 1.0);
}