<button class="start">Start Animation</button>
<h1>Airports in the USA: <span class="usa">___</span></h1>

body {
  margin: 20px;
  font-family: 'Lato';
  font-weight: 300;
  text-align: center;
}

h1 {
  font-size: 3em;
  font-weight: 900;
}

h1 span {
  display: inline-block;
}

.e, .lb {
  position: relative;
  z-index: 99;
}


button {
  background: wheat;
  border: 1px solid black;
  font-family: 'Lato';
  border-radius: 5px;
  padding: 8px;
  margin: 20px 0;
  outline: none;
  cursor: pointer;
}

var usa = document.querySelector(".usa");
var startButton = document.querySelector(".start");

var animateUSA = KUTE.to(
  usa,
  { number: 19536 }
);

startButton.addEventListener(
  "click",
  function() {
    animateUSA.start();
  },
  false
);