19 lines, no comments · 587 tokens, written in 8 seconds for $0.0016

 1  let x, y, vx, vy;
 2  
 3  function setup() {
 4    createCanvas(400, 400);
 5    x = width / 2;
 6    y = height / 2;
 7    vx = 3;
 8    vy = 2;
 9  }
10  
11  function draw() {
12    background(220);
13    fill((frameCount % 255), 150, 200);
14    ellipse(x, y, 50, 50);
15    x += vx;
16    y += vy;
17    if (x > width || x < 0) vx *= -1;
18    if (y > height || y < 0) vy *= -1;
19  }