/*{
  "DESCRIPTION": "Gray-Scott reaction-diffusion that grows liquid coral and ink-like cells.",
  "INPUTS": [
    { "NAME": "feed", "TYPE": "float", "DEFAULT": 0.055, "MIN": 0.010, "MAX": 0.080 },
    { "NAME": "kill", "TYPE": "float", "DEFAULT": 0.062, "MIN": 0.030, "MAX": 0.075 },
    { "NAME": "simSpeed", "TYPE": "float", "DEFAULT": 1.0, "MIN": 0.1, "MAX": 2.0 },
    { "NAME": "seedRate", "TYPE": "float", "DEFAULT": 0.62, "MIN": 0.0, "MAX": 1.0 },
    { "NAME": "colorPhase", "TYPE": "float", "DEFAULT": 0.56, "MIN": 0.0, "MAX": 1.0 }
  ],
  "PASSES": [
    { "TARGET": "chem", "PERSISTENT": true, "FLOAT": true },
    {}
  ]
}*/

#define TAU 6.28318530718

vec3 palette(float t) {
  return 0.52 + 0.48 * cos(TAU * (t + colorPhase + vec3(0.00, 0.18, 0.42)));
}

vec2 chemistry(vec2 uv) {
  return IMG_NORM_PIXEL(chem, uv).rg;
}

void main() {
  vec2 uv = isf_FragNormCoord;

  if (PASSINDEX == 0) {
    vec2 px = 1.0 / RENDERSIZE;
    vec2 c = chemistry(uv);

    if (FRAMEINDEX < 2 || dot(c, c) < 0.000001) {
      vec2 p = uv - 0.5;
      p.x *= RENDERSIZE.x / RENDERSIZE.y;
      float organic = sin(p.x * 31.0) + sin(p.y * 27.0)
                    + sin((p.x + p.y) * 19.0) + sin(length(p) * 43.0);
      float seed = smoothstep(1.65, 2.75, organic)
                 * smoothstep(0.58, 0.12, length(p));
      seed += smoothstep(0.155, 0.115, length(p));
      seed += smoothstep(0.052, 0.028, length(p - vec2(0.23, 0.02)));
      seed += smoothstep(0.052, 0.028, length(p + vec2(0.23, -0.02)));
      seed += smoothstep(0.040, 0.020, length(p - vec2(0.0, 0.25)));
      seed += smoothstep(0.040, 0.020, length(p + vec2(0.0, 0.25)));
      seed = clamp(seed, 0.0, 1.0);
      c = mix(vec2(1.0, 0.0), vec2(0.52, 0.28), seed);
    }

    vec2 lap = -c;
    lap += 0.20 * chemistry(uv + vec2(px.x, 0.0));
    lap += 0.20 * chemistry(uv - vec2(px.x, 0.0));
    lap += 0.20 * chemistry(uv + vec2(0.0, px.y));
    lap += 0.20 * chemistry(uv - vec2(0.0, px.y));
    lap += 0.05 * chemistry(uv + px);
    lap += 0.05 * chemistry(uv - px);
    lap += 0.05 * chemistry(uv + vec2(px.x, -px.y));
    lap += 0.05 * chemistry(uv + vec2(-px.x, px.y));

    float u = c.r;
    float v = c.g;
    float reaction = u * v * v;
    float stepSize = min(TIMEDELTA * 60.0, 1.35) * simSpeed;
    u += (0.16 * lap.r - reaction + feed * (1.0 - u)) * stepSize;
    v += (0.08 * lap.g + reaction - (kill + feed) * v) * stepSize;

    vec2 orbit = vec2(
      0.5 + 0.29 * cos(TIME * 0.31),
      0.5 + 0.21 * sin(TIME * 0.47)
    );
    vec2 od = uv - orbit;
    od.x *= RENDERSIZE.x / RENDERSIZE.y;
    vec2 orbit2 = vec2(
      0.5 + 0.24 * cos(TIME * 0.23 + 3.14159),
      0.5 + 0.31 * sin(TIME * 0.39 + 1.4)
    );
    vec2 od2 = uv - orbit2;
    od2.x *= RENDERSIZE.x / RENDERSIZE.y;
    float freshSeed = smoothstep(0.026, 0.0, length(od));
    freshSeed += 0.8 * smoothstep(0.022, 0.0, length(od2));
    freshSeed = clamp(freshSeed * seedRate, 0.0, 1.0);
    v = max(v, freshSeed * 0.38);
    u = mix(u, 0.52, freshSeed);

    gl_FragColor = vec4(clamp(u, 0.0, 1.0), clamp(v, 0.0, 1.0), 0.0, 1.0);
  } else {
    vec2 c = IMG_THIS_PIXEL(chem).rg;
    float ink = smoothstep(0.012, 0.24, c.g);
    float membrane = smoothstep(0.030, 0.0, abs(c.g - 0.075));
    vec3 col = palette(c.g * 3.4 + c.r * 0.18);
    col *= 0.035 + 1.52 * ink;
    col += membrane * palette(c.r + 0.17) * 0.92;
    col += vec3(0.003, 0.006, 0.014);
    col = col / (1.0 + 0.45 * col);
    gl_FragColor = vec4(col, 1.0);
  }
}