float line(float value, float target, float thickness)
{
    return 1.0 - smoothstep(0.0, thickness, abs(value - target));
}

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

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

    color += vec3(uv.x * 0.25, uv.y * 0.35, 0.45);

    float grid = 0.0;
    grid += line(fract(uv.x * 10.0), 0.0, 0.015);
    grid += line(fract(uv.y * 10.0), 0.0, 0.015);

    float centerX = line(uv.x, 0.5, 0.004);
    float centerY = line(uv.y, 0.5, 0.004);

    color += grid * vec3(0.0, 0.35, 0.75);
    color += (centerX + centerY) * vec3(0.2, 0.9, 1.0);

    fragColor = vec4(color, 1.0);
}