html,
body {
  width: 100%;
  height: 100%;
  margin: 0;
}

.loader {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 15px;
}

.loader .progress {
  width: 0%;
  height: 100%;
  background-color: orange;
}

section {
  width: 70%;
  height: 500px;
  margin: 15px auto;
  display: flex;
  background-color: #eee;
  justify-content: center;
  align-items: center;
  color: #000;
  font-weight: bold;
  font-size: 24px;
}