float map(vec3 p, float bass)
{
    return length(p.xy) - 0.5
           + sin(p.z * 6.0 + iTime) * bass * 0.25;
}

void mainImage(out vec4 fragColor, in vec2 fragCoord)
{
    vec2 uv = fragCoord.xy / iResolution.xy;

    vec2 p = uv * 2.0 - 1.0;

    p.x *= iResolution.x / iResolution.y;

    float bass =
        0.5 +
        0.5 * sin(iTime * 2.5);

    vec3 ro = vec3(0.0, 0.0, iTime * 2.0);
    vec3 rd = normalize(vec3(p, 1.2));

    float d = 0.0;

    vec3 color = vec3(0.0);

    for(int i = 0; i < 64; i++)
    {
        vec3 pos = ro + rd * d;

        float ds = map(pos, bass);

        color += vec3(
            bass,
            0.2,
            1.0
        ) * exp(-abs(ds) * 10.0);

        d += abs(ds) * 0.7;

        if(d > 20.0) break;
    }

    fragColor = vec4(color, 1.0);
}