float x = 100;
float y = 100;
float xspeed = 1;
float yspeed = 3.3;

void setup() {
	size(200,200);
	smooth();
	background(255);
}

void draw() {
	noStroke();
	fill(255,10);
	rect(0,0,width,height);
	x = x + xspeed;
	y = y + yspeed;
	if ((x > width) || (x < 0)) 
		{
			xspeed = xspeed * -1;
		}
	if ((y > height) || (y < 0)) 
		{
			yspeed = yspeed * -1;
		}
	stroke(0);
	fill(175);
	ellipse(x,y,16,16);
}