SketchBook

var rad = 60;
var xpos, ypos;

var xspeed = 240;
var yspeed = 220;

var xdirection = 1;
var ydirection = 1;

function setup() {
createCanvas(windowWidth,
windowHeight);
noStroke();
ellipseMode(RADIUS);

xpos = width / 2;
ypos = height / 2;
}

function draw() {
background(234, 234, 234);
 fill(100, 20, 150);

xpos = xpos + xspeed * xdirection;
ypos = ypos + yspeed * ydirection;

if (xpos > width - rad || xpos < rad) {
xdirection *= -1;
}

if (ypos > height - rad || ypos < rad) {
ydirection *= -1;
}

ellipse(xpos, ypos, rad, rad);
}