如何用for，能画出多个这样的圆啊，试了半天感觉方向都不太对。。
float x=50.0;
float y=50.0;
float radius=15.0;
float speedX=1.0;
float speedY=0.4;
int directionX=1;
int directionY=-1;
void setup(){
size(500,500);
smooth();
noStroke();
ellipseMode(RADIUS);
}
void draw(){
fill(0,12);
rect(0,0,width,height);
fill(255);
ellipse(x,y,radius,radius);
x+=speedX*directionX;
if((x>width-radius)||(x<radius)){
directionX=-directionX;
}
y+=speedY*directionY;
if((y>height-radius)||(y<radius)){
directionY=-directionY;}
}