float theta;
float x, y, d = 0.01;

float arcsin3(float x){
  return (1.025*(x+pow(x,3)/6));
}

float arcsin1(float x){
  return (1.11*x);
}

void setup(){
  size(600,600);
  theta = 0;
  noStroke();
}

void draw(){
  translate(300,300);
  rotate(-PI/2);
  
  x = cos(theta);
  y = sin(theta);
  
  if(theta < 0.01){
    d = 0.01;
  }else if(theta > 2*PI - 0.01){
    d = -0.01;
  }
  theta += d;
  background(0);
  fill(0xFF*4/4);
  arc(0,0,480,480,0,theta);
  
  fill(0xFF*3/4);
  if(arcsin3(y)>PI/4){
    arc(0,0,400,400,0, PI*1/2-arcsin3(x) );
  }else if(arcsin3(y)<-PI/4){
    arc(0,0,400,400,0, PI*3/2+arcsin3(x) );
  }else if(x>0){
    if(y>0){
      arc(0,0,400,400,0, arcsin3(y) );
    }else{
      arc(0,0,400,400,0, 2*PI+arcsin3(y) );
    }
  }else{
    arc(0,0,400,400,0, PI-arcsin3(y) );
  }
  
  fill(0xFF*2/4);
  if(arcsin1(y)>PI/4){
    arc(0,0,320,320,0, PI*1/2-arcsin1(x) );
  }else if(arcsin1(y)<-PI/4){
    arc(0,0,320,320,0, PI*3/2+arcsin1(x) );
  }else if(x>0){
    if(y>0){
      arc(0,0,320,320,0, arcsin1(y) );
    }else{
      arc(0,0,320,320,0, 2*PI+arcsin1(y) );
    }
  }else{
    arc(0,0,320,320,0, PI-arcsin1(y) );
  }
  
  fill(0xFF*1/4);
  if(x>0){
    if(y>0){
      arc(0,0,240,240,0, asin(y) );
    }else{
      arc(0,0,240,240,0, 2*PI+asin(y) );
    }
  }else{
    arc(0,0,240,240,0, PI-asin(y) );
  }
}