float x; float y; void setup() { size(400, 400); smooth(); background(255); noStroke(); x = width / 2; y = height / 2; } void draw() { fadeBackground(); x = x + random(-5, 5); x = constrain(x, 0, width); y = y + random(-5, 5); y = constrain(y, 0, height); fill(x, y, 0); ellipse(x, y, 40, 40); } void fadeBackground() { fill(255, 10); rect(0, 0, width, height); }