[SFML GLSL] Fragment Shader - Okręgi

void main() {
 vec2 st = (2.*gl_TexCoord[0].xy * u_resolution.x - u_resolution.xy ) / u_resolution.y;
 st *= 10.;
 vec2 F = cellular2x2x2(vec3(st,u_time));
 float n = smoothstep(0.4, 0.5, F.x);

 vec3 background = vec3(0.2, 0.4, 0.05);
 vec3 bubble_color = vec3(0.56, 0.59, 0.07);

 vec3 final_color = mix(bubble_color, background, n);

 gl_FragColor = vec4(final_color, 1.0);
}