SOURCE

var x=200,y=200;
var sx=2,sy=3;
function setup() { 
    createCanvas(400, 400);
} 
function draw() { 
    background(87,250,255);
    ellipse(x,y,20,20);
    x+=sx;
    y+=sy;
    if(x>width||x<0){
        sx*=-1;
    }
    if(y>height||y<0){
        sy*=-1;
    }
}

function setup() { 
	createCanvas(400, 400);
}
var x=200,y=200;
function draw() { 
    background(87,250,255);
    ellipse(x,y,20,20);
}
var sx=2,sy=3;
function draw() { 
    background(87,250,255);
    ellipse(x,y,25,20);
    x+=sx;
    y+=sy;
}