#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;

float random (in vec2 st) { 
    return fract(sin(dot(st.xy,
                         vec2(12.9898,78.233)))* 
        43758.5453123);
}

float noise (in vec2 st) {
    vec2 i = floor(st);
    vec2 f = fract(st);

    float a = random(i);
    float b = random(i + vec2(1.0, 0.0));
    float c = random(i + vec2(0.0, 1.0));
    float d = random(i + vec2(1.0, 1.0));

    vec2 u = f * f * (3.0 - 2.0 * f);

    return mix(a, b, u.x) + 
            (c - a)* u.y * (1.0 - u.x) + 
            (d - b) * u.x * u.y;
}

#define OCTAVES 10
float fbm (in vec2 st) {
    float value = 0.0;
    float amplitud = .5;
    float frequency = 0.;
    
    for (int i = 0; i < OCTAVES; i++) {
        value += amplitud * noise(st);
        st *= 2.;
        amplitud *= .7;
    }
    return value;
}


vec3 circle(in vec2 _st, in float _radius, vec3 color){
    vec2 dist = _st-vec2(0.5);
    return color-smoothstep(_radius-(_radius*0.02),
                         _radius+(_radius*0.02),
                         dot(dist,dist)*4.0);
}

void main() {
    vec2 st = gl_FragCoord.xy/u_resolution.xy;
    st*=5.;
    st.x *= u_resolution.x/u_resolution.y;

    vec3 color = vec3(0.);
    color += fbm(st*3.0);
    float resmin = min(u_resolution.x, u_resolution.y);
    color -=  smoothstep(0.44, 0.48, distance(gl_FragCoord.xy/resmin, (u_resolution/2.)/resmin));

    
    

    gl_FragColor = vec4(color,1.0);
}