// Author @patriciogv - 2015
// http://patriciogonzalezvivo.com

#ifdef GL_ES
precision mediump float;
#endif

#define PI 3.14159265359
#define TWO_PI 6.28318530718

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

float shape(vec2 st, int N){
    st = st *2.-1.;
    float a = atan(st.x,st.y)+PI;
    float r = TWO_PI/float(N);
    return cos(floor(.5+a/r)*r-a)*length(st);
}

void main(){
  vec2 st = gl_FragCoord.xy/u_resolution.xy;
  st.x *= u_resolution.x/u_resolution.y;
  vec3 color = vec3(0.0);
  float d = 0.0;
  
  d = min(shape(st,3),shape(st+vec2(0.,0.2),4));
    
  gl_FragColor = vec4(vec3(1.0-smoothstep(.2,.25,d)),1.0);
}