I'm drawing animated circles inside a canvas, and so far I managed to make it go from left to right inside the canvas. What I need to do is, when the circle reaches it's righmost position, to make it start its path (left to right) again, but in a position below. I'm trying to change it's y position by at least the circle's diameter, so far without success. Any insight on how can I achieve this? Is it better to make it part of the animation, or make the left-right movement a simple loop with a y position change at the end? My code so far is the following:

var canvas3 = document.getElementById("canvas3");

canvas3.width = 300;
canvas3.height = 500;

var c3 = canvas3.getContext("2d");

var radius = 13;
var x = radius;
var y = radius;

var dx = 1;
var dy = 0;

function animate3() {
  requestAnimationFrame(animate3);

  c3.clearRect(0, 0, 300, 500);

  if (x + radius > 300 || x - radius < 0) {
    dx = 0;
    y + y;
  }

  if (y + radius > 500 || y - radius < 0) {
    dy = 0;
  }

  x += dx;
  y += dy;

  c3.beginPath();
  c3.arc(x, y, 12, 0, Math.PI * 2, false);
  c3.stroke();
  c3.fillText(5, x - 3, y + 3);
}

animate3();