#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;

void main() {
  vec2 st = gl_FragCoord.xy/u_resolution.xy;
  st.x *= u_resolution.x/u_resolution.y; //wtf is this for? maybe it's to maintain aspect ratio
  vec3 color = vec3(0.0);
  float d = 0.0;
  //Remap the space to -1 to 1
  st = st*2.-1.;

  // number of sides of your shape 
  int N = 3;


  // angle and radius from the current pixel
  float a = atan(st.x,st.y)+PI;
  float r = TWO_PI/float(N);
  d = cos(floor(.5+a/r)*r-a)*length(st);

  color = vec3(1.0-smoothstep(.4,.41,d));

  gl_FragColor = vec4(color,1.0);
}