/*{
  "DESCRIPTION": "Neon seen through rippling liquid glass: a field of thin neon ribbons refracted by a procedural wave surface, bent and smeared by the surface gradient, split into red/green/blue by chromatic dispersion, with hot caustic glints riding the wave crests. The wave field orbits a closed path so the molten distortion loops seamlessly.",
  "CREDIT": "glslop agent (Claude)",
  "CATEGORIES": ["refraction", "distortion", "caustics", "glass", "2d"],
  "INPUTS": [
    { "NAME": "speed",   "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.0, "MAX": 3.0 },
    { "NAME": "refract", "TYPE": "float", "DEFAULT": 0.045,"MIN": 0.0, "MAX": 0.2 },
    { "NAME": "ripple",  "TYPE": "float", "DEFAULT": 2.2,  "MIN": 1.0, "MAX": 6.0 },
    { "NAME": "hue",     "TYPE": "float", "DEFAULT": 0.6,  "MIN": 0.0, "MAX": 1.0 },
    { "NAME": "chroma",  "TYPE": "float", "DEFAULT": 1.0,  "MIN": 0.0, "MAX": 2.0 }
  ]
}*/

#define PI  3.14159265359
#define TAU 6.28318530718
const float PERIOD = 16.0;

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 vnoise(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);
}

// glowing neon grid on a dark field -> refraction reads as bending lines
vec3 bg(vec2 p){
  vec2 q = p*5.0;
  float dx = abs(fract(q.x + 0.5) - 0.5);
  float dy = abs(fract(q.y + 0.5) - 0.5);
  float lx = 0.012 / (dx*dx + 0.012);                       // glowing vertical lines
  float ly = 0.012 / (dy*dy + 0.012);                       // glowing horizontal lines
  float node = lx * ly;                                     // bright cell corners
  float hs = hue + 0.05*q.x + 0.04*q.y;                     // hue drifts across the grid
  vec3 col = vec3(0.015, 0.01, 0.04);                       // dark base
  col += pal(hs)        * lx * 0.9;
  col += pal(hs + 0.3)  * ly * 0.9;
  col += vec3(1.0, 0.95, 1.0) * pow(node, 0.7) * 0.5;       // hot intersections
  return col;
}

// wave height field (orbiting offset -> seamless loop)
float waveH(vec2 p, float th){
  vec2 o1 = 0.35*vec2(cos(th), sin(th));
  vec2 o2 = 0.30*vec2(cos(2.0*th + 1.0), sin(2.0*th + 1.0));
  float h = vnoise(p*ripple + o1*ripple);
  h += 0.5*vnoise(p*ripple*2.1 - o2*ripple);
  h += 0.18*sin(p.x*ripple*3.3 + th*2.0) * cos(p.y*ripple*2.7 - th*2.0);
  return h;
}

void main(){
  vec2 uv = (2.0*gl_FragCoord.xy - RENDERSIZE.xy) / RENDERSIZE.y;

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

  // gradient of the wave surface -> refraction direction
  vec2 e = vec2(0.005, 0.0);
  float hx = waveH(uv + e.xy, th) - waveH(uv - e.xy, th);
  float hy = waveH(uv + e.yx, th) - waveH(uv - e.yx, th);
  vec2 grad = vec2(hx, hy) / (2.0*e.x);

  vec2 disp = refract * grad;

  // chromatic dispersion: sample the backdrop with per-channel offsets
  float cd = 0.10 * chroma;
  vec3 col;
  col.r = bg(uv + disp*(1.0 + cd)).r;
  col.g = bg(uv + disp).g;
  col.b = bg(uv + disp*(1.0 - cd)).b;

  // caustic glints on the wave crests (steep gradient = bright, tight + hot)
  float crest = length(grad);
  float glint = smoothstep(2.2, 4.5, crest);
  col += vec3(1.0, 0.97, 0.9) * pow(glint, 2.0) * 0.6;

  // a faint glassy sheen following the surface height
  float sheen = waveH(uv, th);
  col *= 0.85 + 0.25*smoothstep(0.2, 1.6, sheen);

  col *= 1.0 - 0.14*dot(uv, uv);
  col = col / (1.0 + col);
  col = pow(col, vec3(0.85));
  gl_FragColor = vec4(col, 1.0);
}