@vs vert
in vec3 a_pos;

uniform float radius;
uniform vec2 coord;
uniform mat4 vp;
out vec2 coords;
out float rad;
void main() {
  vec3 pos = a_pos;
  pos.xy -= 0.5;
  pos.xy *= 2;
  coords = pos.xy;
  pos *= radius;
  pos.xy += coord;
  rad = radius;
  gl_Position = vp * vec4(pos,1);
}
@end

@fs frag
in vec2 coords;
in float rad;
uniform vec4 shade;
uniform float inner_r;
out vec4 color;
void main() {
  float px = 1/rad;
  float blur = 1.0+px;
  float R = 1;
  float R2 = 1-inner_r;
  float dist = distance(vec2(0,0),coords);
  float sm = 1 - smoothstep(R-px,R*blur,dist);
  float sm2 = smoothstep(R2-px,R2*blur,dist);
  
  float alpha = sm*sm2;
  color = vec4(shade.xyz, alpha*shade.a);
}
@end

@program circle vert frag