<div class="App">
  <h1>Step 3</h1>

  <div class="Example">
    <div>3. setTimeout with delta fix (100ms)</div>
    <div class="Example-position"></div>
    <div class="Box"></div>
  </div>
</div>

* {
  box-sizing: border-box;
}

body {
  background: #fdfdfd;
  font-family: Helvetica, Arial, sans-serif;
}

.App {
  position: relative;
  max-width: 400px;
  margin: 0 auto;
  padding: 40px 20px;
}

h1 {
  font-size: 1.2em;
  font-weight: bold;
  margin-bottom: 5px;
}

a {
  color: #409ad7;
  text-decoration: none;
  border-bottom: 1px solid #ddd;
  margin-bottom: 20px;
  display: inline-block;
  
  &:hover {
    border-bottom-color: #409ad7;
  }
}

.Example {
  border: 1px solid #ddd;
  border-radius: 3px;
  background: #fff;
  padding: 20px;
  margin-bottom: 10px;
}

.Example-position {
  margin-top: 5px;
  color: #409ad7;
}

.Box {
  width: 30px;
  height: 30px;
  background: #34ba9c;
  margin-top: 20px;
  border-radius: 2px;
}

const FRAME_DURATION = 1000 / 60; // 60fps frame duration
// If available we are using native "performance" API instead of "Date"
// It it's name suggests it is more performant, read more on MDN:
// https://developer.mozilla.org/en-US/docs/Web/API/Performance
const getTime = typeof performance === 'function' ? performance.now : Date.now;
const MAX_POSITION = 150;

const box = document.querySelector('.Box');
// Initial position
let position = 0;
// Initial time
let lastUpdate = getTime();

function animate() {
  const now = getTime();
  // This is the main part
  // We are checking how much time has passed since the last update
  // and translating that to frames
  const delta = (now - lastUpdate) / FRAME_DURATION;

  // Updating scene logic
  // We want to move the box 1px per each 16.66ms (60fps)
  // so we are multipling 1px with the number of frames passed
  position += 1 * delta;
  
  // Reset position
  if (position > MAX_POSITION) {
    position -= MAX_POSITION;
  }

  // Render updated scene
  box.style.transform = `translateX(${ position }px)`;

  // Update last updated time
  lastUpdate = now;

  // Fake 10fps using "setTimeout"
  setTimeout(animate, 100);
}

animate();