// Slow colourful ocean for the chaos event: the palette drifts through the
// whole colour wheel over a few minutes, jellyfish glide along the stairs,
// plankton fades in and out. Nothing here moves fast.

float hash(float n) { return fract(sin(n * 12.9898) * 43758.5453); }

vec3 hsv(float h, float s, float v) {
    vec3 rgb = clamp(abs(mod(h * 6.0 + vec3(0.0, 4.0, 2.0), 6.0) - 3.0) - 1.0,
                     0.0, 1.0);
    return v * mix(vec3(1.0), rgb, s);
}

// A jellyfish: soft blob that glides and breathes
vec3 jelly(float i, float t, float seed) {
    float pos = 6.0 + 5.5 * sin(t * (0.07 + 0.03 * seed) + seed * 4.0);
    float d = i - pos;
    float breath = 0.55 + 0.45 * sin(t * 0.5 + seed * 3.0);
    float hue = 0.85 + 0.35 * seed + t / 180.0;      // contrasts with the water
    return hsv(hue, 0.7, 1.0) * exp(-d * d * 0.55) * breath * 0.75;
}

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    float i = floor(fragCoord.x / iResolution.x * 16.0);
    float t = iTime;

    // waves, all slow
    float w1 = 0.5 + 0.5 * sin(i * 0.55 - t * 0.45);
    float w2 = 0.5 + 0.5 * sin(i * 0.90 + t * 0.30 + 1.0);
    float w3 = 0.5 + 0.5 * sin(i * 0.25 - t * 0.17 + 2.5);
    float h = 0.45 * w1 + 0.30 * w2 + 0.25 * w3;

    // water colour: blue to magenta to teal, wheel drifts over 3 minutes
    float hue = 0.58 + 0.22 * sin(i * 0.22 + t * 0.06) + 0.10 * h + t / 180.0;
    vec3 col = hsv(hue, 0.95, 0.10 + 0.75 * h);

    // foam on the crests
    float foam = smoothstep(0.80, 0.97, h);
    col = mix(col, vec3(0.9), foam * 0.7);

    // jellyfish
    col += jelly(i, t, 0.0) + jelly(i, t, 1.0);

    // plankton, each step lights up now and then for ~12 s
    float cyc = t * 0.08 + hash(i);
    float cell = floor(cyc);
    float life = sin(3.14159265 * fract(cyc));
    float on = step(0.72, hash(i * 13.0 + cell));
    col += hsv(hue + 0.5, 0.4, 1.0) * pow(life, 4.0) * on * 0.55;

    fragColor = vec4(col, 1.0);
}