#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 random(float x) {
    return fract(sin(x)*10000.);
}

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;
}

float box(vec2 _st, vec2 _size, float _smoothEdges){
    _size = vec2(0.5)-_size*0.5;
    vec2 aa = vec2(_smoothEdges*0.5);
    vec2 uv = smoothstep(_size,_size+aa,_st);
    uv *= smoothstep(_size,_size+aa,vec2(1.0)-_st);
    return uv.x*uv.y;
}

void main() {
    vec2 st_ = gl_FragCoord.xy/u_resolution.xy;
    st_.x *= 3.;
    vec2 st = fract(st_);
    vec4 color = vec4(0.);

    if (st_.x < 1.) {
      color = vec4(random(1.), 0., 0.,1.)*box(st,vec2(1.),0.3);
    } else if (st_.x > 2.) {
      color = vec4(0.0, 0.6, 0.3,1.)*box(st,vec2(1.1),0.7)+vec4(0.6, 0., 0.,0.6)*box(st,vec2(1.1),0.4);
    } else {
      color = vec4(0.6, 0., 0.,1.)*box(st,vec2(1.1),0.3);
    }

    st_.x /= 3.;
    st_ *= 10.;
    for (float i=0.;i<100.;i++) {
        color += noise(st_*i)*0.03 * (random(st_*i) > 0.5 ? -1. : 1.);
    }

    gl_FragColor = vec4(color);
}