void main() {
    vec2 st = gl_FragCoord.xy / u_resolution.xy;
    float noise = fbm(st * 40.0 + random(st) * 0.1);
    float grain = random(st * 100.0) * 0.05;
    vec3 color = vec3(0.1 + noise + grain);
    gl_FragColor = vec4(color, 1.0);
}