/*{
  "DESCRIPTION": "The Witness: a vast alien eye watching from the dark. Its iris is woven from thousands of glowing fibres around a black void pupil that dilates and breathes; the gaze drifts on a closed path and a wet catch-light slides across the cornea. Everything cycles on integer harmonics for a seamless 16s loop.",
  "CREDIT": "glslop agent (Claude)",
  "CATEGORIES": ["eye", "organic", "surreal", "neon", "bizarre"],
  "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": "fibers", "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.4, "MAX": 2.0 },
    { "NAME": "zoom",   "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.6, "MAX": 1.8 }
  ]
}*/

#define PI  3.14159265359
#define TAU 6.28318530718

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 hash(vec2 p){ return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453); }
float noise(vec2 p){
  vec2 i = floor(p), f = fract(p); f = f * f * (3.0 - 2.0 * f);
  float a = hash(i), b = hash(i + vec2(1, 0)), c = hash(i + vec2(0, 1)), d = hash(i + vec2(1, 1));
  return mix(mix(a, b, f.x), mix(c, d, f.x), f.y);
}
float fbm(vec2 p){ float s = 0.0, a = 0.5; for (int i = 0; i < 4; i++){ s += a * noise(p); p *= 2.0; a *= 0.5; } return s; }

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

  float ph = fract(TIME * speed / PERIOD);
  float th = TAU * ph;

  // gaze drifts on a closed Lissajous (seamless)
  vec2 gaze = 0.10 * vec2(sin(th), sin(2.0 * th) * 0.6);
  vec2 p = uv - gaze;
  float r = length(p);
  vec2  dir = p / max(r, 1e-4);
  float ang = atan(p.y, p.x);

  float pupilR = 0.17 + 0.05 * sin(th);          // dilation (breathing)
  float irisR  = 0.62;

  vec3 col = vec3(0.0);

  // --- iris fibres (between pupil and limbus) ---
  float t = clamp((r - pupilR) / (irisR - pupilR), 0.0, 1.0);   // 0 at pupil, 1 at rim
  // organic radial fibres; integer angular frequency -> no seam
  float warp = fbm(dir * 3.0 + r * 2.0);
  float f = 0.5 + 0.5 * sin(ang * 160.0 * fibers + 16.0 * warp + r * 10.0);
  f = pow(f, 2.0);
  float crypt = smoothstep(0.25, 0.8, fbm(dir * 5.0 + 7.3));     // darker patches
  // collarette: a brighter ring partway out
  float collar = exp(-pow((t - 0.35) * 6.0, 2.0));

  vec3 irisCol = mix(pal(hue + 0.55), pal(hue + 0.92), t);        // warm centre -> cool rim
  irisCol = mix(vec3(dot(irisCol, vec3(0.33))), irisCol, 1.4);    // boost saturation
  float irisBright = (0.35 + 1.25 * f) * (0.5 + 0.7 * crypt) + collar * 1.8;
  float irisMask = smoothstep(pupilR, pupilR + 0.02, r) * smoothstep(irisR, irisR - 0.05, r);
  col += irisCol * irisBright * irisMask * 1.4 * glow;

  // limbus: dark ring at the iris edge
  col *= 1.0 - 0.8 * exp(-pow((r - irisR) * 26.0, 2.0));

  // --- pupil: black void with a faint inner rim glow ---
  float pupilEdge = smoothstep(pupilR, pupilR - 0.03, r);
  col = mix(col, vec3(0.0), pupilEdge);
  col += pal(hue + 0.5) * exp(-pow((r - pupilR) * 30.0, 2.0)) * 0.6 * glow;  // rim light on pupil

  // --- sclera / surrounding darkness with faint veins ---
  float outside = smoothstep(irisR, irisR + 0.04, r);
  float veins = smoothstep(0.55, 0.9, fbm(uv * 4.0 + 3.0));
  vec3 scler = vec3(0.04, 0.05, 0.07) + pal(hue + 0.0) * veins * 0.12;
  col = mix(col, scler, outside);

  // --- wet catch-light (specular) sliding across the cornea ---
  vec2 cl = vec2(-0.17, 0.19) + 0.04 * vec2(cos(th), sin(th));
  float spec = exp(-dot(uv - cl, uv - cl) * 260.0);
  col += vec3(1.0) * spec * 2.4;                    // tight glossy highlight
  col += vec3(1.0) * exp(-dot(uv - cl, uv - cl) * 40.0) * 0.5;   // soft bloom around it
  // small second highlight
  vec2 cl2 = cl * 0.45 - vec2(0.04, -0.02);
  col += vec3(0.85, 0.92, 1.0) * exp(-dot(uv - cl2, uv - cl2) * 600.0) * 1.0;

  col = col / (1.0 + col);
  col = pow(col, vec3(0.85));
  col *= 1.0 - 0.25 * dot(uv * zoom, uv * zoom);

  gl_FragColor = vec4(col, 1.0);
}