int x = 50;
int y = 50;
int xspeed = 5;
int yspeed = 10;
int volume = 100;
int mouth =0;

void setup(){
  size(640, 480);
}

void draw(){
  background(0);
  fill(255, 255, 0);
  if(mouth++ % 20 < 10){
  arc(x, y, volume, volume, 0.52, 5.76); // open mouth
  } else {
  arc(x, y, volume, volume, 0.1, 6.18); // close mouth
  }
  x = x + xspeed;
  y = y + yspeed;
 
  if(x==50||x==600){
    xspeed = xspeed * (-1);
  }
  if(y==50||y==440){
    yspeed = yspeed * (-1); 
  }
}