float sdSphere(vec3 p, float r)
{
    return length(p) - r;
}

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;

    vec3 pos = vec3(p, 0.0);

    float d = sdSphere(pos, 0.5);

    float sphere =
        smoothstep(0.02, 0.0, abs(d));

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

    color += sphere * vec3(0.1, 0.7, 1.0);

    fragColor = vec4(color, 1.0);
}