/*{
  "DESCRIPTION": "Plexus — drifting points knitting and unknitting a constellation web of faint light in the deep.",
  "CREDIT": "claude-opus-4-8",
  "INPUTS": [
    { "NAME": "link",  "TYPE": "float", "DEFAULT": 0.6, "MIN": 0.3, "MAX": 1.0 },
    { "NAME": "size",  "TYPE": "float", "DEFAULT": 0.02, "MIN": 0.008, "MAX": 0.05 },
    { "NAME": "glow",  "TYPE": "float", "DEFAULT": 0.8, "MIN": 0.2, "MAX": 1.6 },
    { "NAME": "tint",  "TYPE": "float", "DEFAULT": 0.5, "MIN": 0.0, "MAX": 1.0 }
  ]
}*/

float hash(vec2 p){ p = fract(p * vec2(123.34, 456.21)); p += dot(p, p + 45.32); return fract(p.x * p.y); }
vec2 pos(float i, float t){
  return 0.85 * vec2(sin(i * 1.7 + t * 0.20), cos(i * 2.3 + t * 0.15))
       + 0.32 * vec2(sin(i * 0.7 + t * 0.11), cos(i * 1.1 - t * 0.13));
}

float distSeg(vec2 p, vec2 a, vec2 b){
  vec2 pa = p - a, ba = b - a;
  float h = clamp(dot(pa, ba) / dot(ba, ba), 0.0, 1.0);
  return length(pa - ba * h);
}

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

  vec3 cyan = mix(vec3(0.2, 0.8, 1.0), vec3(0.4, 0.5, 1.0), tint);
  vec3 col = mix(vec3(0.0, 0.025, 0.06), vec3(0.0, 0.005, 0.02), length(uv));   // deep-sea field
  // faint plankton/starfield for depth
  float st = hash(floor(gl_FragCoord.xy));
  col += smoothstep(0.992, 1.0, st) * (0.3 + 0.3 * sin(t * 2.0 + st * 40.0)) * cyan * 0.8;
  float lines = 0.0, dots = 0.0;

  const int N = 28;
  for (int i = 0; i < N; i++){
    vec2 a = pos(float(i), t);
    float da = length(uv - a);
    dots += smoothstep(size, size * 0.2, da);                 // crisp node
    dots += exp(-da * da / (size * size * 12.0)) * 0.4;       // halo

    for (int j = 0; j < N; j++){
      if (j <= i) continue;
      vec2 b = pos(float(j), t);
      float d = length(a - b);
      if (d < link){
        float seg = distSeg(uv, a, b);
        lines += smoothstep(0.006, 0.0, seg) * smoothstep(link, link * 0.4, d);  // faint link, fades with length
      }
    }
  }

  col += cyan * lines * 0.5 * glow;
  col += cyan * dots * (0.6 + 0.6 * glow);
  col += vec3(0.8, 0.95, 1.0) * pow(dots, 3.0) * 0.5;          // bright node cores

  col *= 1.0 - 0.3 * dot(uv, uv);
  col = col / (1.0 + 0.5 * col);
  col = pow(max(col, 0.0), vec3(0.88));
  gl_FragColor = vec4(col, 1.0);
}