var y = 0;

var speed = 3; 

​

function setup() {

  createCanvas(400, 400);

}

​

​

function draw() {

  background(220,100,0);

  stroke(50);

  fill(255,0,210);

  ellipse(x, y, 24, 24);

  x = x + random(-1, 1);

  if(y > 400){     // NOT WORKED, WHY?

   speed = speed * -1;

  }

  console.log(y);

  y = y + speed; //3  > -3

}

​

​

​