// Author @patriciogv ( patricio.io ) - 2015
// Inspired by the Patterns of Nina Warmerdam ( www.behance.net/ninawarmerdam )
#ifdef GL_OES_standard_derivatives
#extension GL_OES_standard_derivatives : enable
#endif

#ifdef GL_ES
precision mediump float;
#endif

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

float aastep(float threshold, float value) {
  #ifdef GL_OES_standard_derivatives
    float afwidth = length(vec2(dFdx(value), dFdy(value))) * 0.70710678118654757;
    return smoothstep(threshold-afwidth, threshold+afwidth, value);
  #else
    return step(threshold, value);
  #endif
}
vec2 brickTile(vec2 st, float zoom){
  st *= zoom;
  if (fract(st.y * 0.5) > 0.5){
      st.x += 0.5;
  }
  return fract(st);
}
float circleDF(vec2 st){
  vec2 pos = vec2(0.5)-st;
  return dot(pos,pos)*3.14;
}
float circle(vec2 st, float radius){
  radius *= 0.75;
  return 1.-aastep(radius,circleDF(st));
}

float dots(vec2 st, float size){
    st = brickTile(st, 2.);
    return circle(st, size);
}

float dotsDF(vec2 st){
    st = brickTile(st, 2.);
    return circleDF(st);
}

void main(){
    vec2 st = gl_FragCoord.xy/u_resolution.xy;
    st.x *= u_resolution.x/u_resolution.y;
    vec3 color = vec3(0.0);

    vec2 IN = st;
    vec2 OUT = st*2.;

    float pct = 1.0-fract(u_mouse.y/u_resolution.y);
    pct = pow(pct,6.);

    float d = 0.0;
    // d = mix(dots(fract(IN),(1.-pct)), dots(fract(OUT),pct), pct);
    // d = mix(dotsDF(fract(IN)), dotsDF(fract(OUT)), pct);
    d = dotsDF(fract(IN))*(1.-pct) + dotsDF(fract(OUT))*pct;
    d = aastep(.21,d);
    color = vec3(d);

    gl_FragColor = vec4(color,1.0);
}