// reappear at left var cx; var cy; var diam = 48; var sign = 1; // -1 or 1 function setup() { var cnv = createCanvas(400, 300); cnv.position(60, 200); cx = width/2; cy = height/2; } //setup function draw() { background(192); strokeWeight(1); stroke(0); fill(255, 0, 0); cx = cx + sign; if (cx >= width - diam/2) { sign = -1; } if (cx <= 0 + diam/2) { sign = 1; } ellipse(cx, cy, diam, diam); } //draw