08160084

fill(#FAFF00);
arc(50,50,80,80,radians(45),radians(315),PIE);

void setup()
{
  size(600,200);
}
int a=20;
int diff=1;
void draw()
{
  background(0); //黑色背景
  fill(#FAE600);
  arc(50,50,80,80,radians(a),radians(360-a),PIE);
  a+=diff;
  if(a>60)diff=-1;//如果角度太大,就改成-1
  if(a<=0)diff=+1;//如果角度太小,就改成-1
}