https://medium.com/@remarkablemark/bouncing-dvd-logo-c8e587c7c473

sketch.js

function checkBoundaryCollision(image) {
  var hasCollision = false;
  // left or right collision
  if (position.x < 0 || position.x + image.width > width) {
    velocity.x *= -1;
    hasCollision = true;
  }
  // top or bottom collision
  if (position.y < 0 || position.y + image.height > height) {
    velocity.y *= -1;
    hasCollision = true;
  }
  return hasCollision;
}