void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 uv = fragCoord / iResolution.xy;
    float wave = 0.5 + 0.5 * sin(iTime + uv.x * 6.2831853);
    vec3 deep = vec3(0.015, 0.025, 0.07);
    vec3 light = vec3(0.08, 0.65, 0.78);
    vec3 color = mix(deep, light, wave * (0.35 + 0.65 * uv.y));
    float glow = exp(-8.0 * dot(uv - 0.5, uv - 0.5));
    color += vec3(0.25, 0.08, 0.35) * glow;
    fragColor = vec4(color, 1.0);
}