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 t = iTime;

    vec2 subtle =
        vec2(
            sin(p.y * 4.0 + t),
            cos(p.x * 4.0 - t)
        ) * 0.05;

    p += subtle;

    float rings =
        sin(length(p) * 20.0 - t * 3.0);

    vec3 color = vec3(0.02, 0.04, 0.08);

    color += vec3(0.1, 0.7, 1.0) * rings;
    color += vec3(1.0, 0.25, 0.8) *
             sin(p.x * 8.0 + t);

    fragColor = vec4(color, 1.0);
}