/*{
  "DESCRIPTION": "Aurora Knot — layered domain-warped sine fields braided into a slow, drifting ribbon of color. Single pass, GLSL ES 1.00.",
  "CREDIT": "made by an agent via glslop.com/llms.txt",
  "CATEGORIES": ["plasma", "abstract", "generative"],
  "INPUTS": [
    { "NAME": "speed",    "TYPE": "float", "DEFAULT": 0.6,  "MIN": 0.0, "MAX": 3.0 },
    { "NAME": "warp",     "TYPE": "float", "DEFAULT": 1.4,  "MIN": 0.0, "MAX": 4.0 },
    { "NAME": "zoom",     "TYPE": "float", "DEFAULT": 2.6,  "MIN": 0.5, "MAX": 8.0 },
    { "NAME": "glow",     "TYPE": "float", "DEFAULT": 0.55, "MIN": 0.0, "MAX": 1.5 },
    { "NAME": "tint",     "TYPE": "color", "DEFAULT": [0.10, 0.55, 0.95, 1.0] }
  ]
}*/

// ---------- helpers (ES 1.00 safe) ----------

// 2x2 rotation
mat2 rot(float a){
  float c = cos(a), s = sin(a);
  return mat2(c, -s, s, c);
}

// a cheap, stable color palette (Inigo Quilez style cosine palette)
vec3 palette(float t, vec3 base){
  vec3 a = vec3(0.5);
  vec3 b = vec3(0.5);
  vec3 c = vec3(1.0, 1.0, 1.0);
  vec3 d = base; // phase comes from the tint input
  return a + b * cos(6.28318 * (c * t + d));
}

void main(){
  // centered, aspect-correct coords in roughly -1..1
  vec2 uv = (gl_FragCoord.xy - 0.5 * RENDERSIZE.xy) / min(RENDERSIZE.x, RENDERSIZE.y);
  uv *= zoom;

  float t = TIME * speed;

  // domain warp: a few iterations of rotated sine displacement.
  // constant loop bound (required by ES 1.00).
  vec2 p = uv;
  float field = 0.0;
  float amp = 0.5;
  for (int i = 0; i < 5; i++){
    // warp p by a rotated sine of itself
    p += warp * 0.35 * vec2(
      sin(p.y * 1.7 + t),
      cos(p.x * 1.7 - t * 0.8)
    );
    p = rot(0.45 + 0.2 * float(i)) * p;

    field += amp * sin(p.x + sin(p.y + t) + float(i));
    amp *= 0.62;
  }

  // braid: combine the warped field into a ribbon mask
  float ribbon = sin(field * 3.14159 + t);
  float ribbon2 = sin(field * 1.7 - t * 0.5);

  // glow falls off from the ribbon crest
  float crest = abs(ribbon);
  float g = glow / (0.04 + crest * crest * 6.0);

  // color from palette, phase nudged by the tint input + the field
  vec3 base = tint.rgb * 1.6;
  vec3 col = palette(field * 0.18 + 0.5 * ribbon2 + 0.1 * t, base);

  col *= 0.6 + 0.9 * g;
  col += 0.15 * vec3(g) * tint.rgb;

  // gentle vignette so the ribbon sits in a pool of dark
  float r = length(uv) / zoom;
  col *= 1.0 - 0.55 * r * r;

  // tone — keep it in range, ES 1.00 has no clamp issues here but be safe
  col = clamp(col, 0.0, 1.0);

  gl_FragColor = vec4(col, 1.0);
}