var y = 150; 

function setup() {

  createCanvas(300, 300);

  x = random(300);

  y = random(300);

​

}

​

function draw() {

  background(220);

  ellipse(x,y, 30, 30);

  x = x - 5; 

  if( x < 0) {

    x = random(300,1000); 

    y = random(300);

  }

}