body,
html {
  height: 100%;
  margin: 0;
  font-family: Arial, sans-serif;
  display: flex;
  flex-direction: column;
  /* stack vertically */
  justify-content: center;
  align-items: center;
  background: #f05e40;
  /* Use any background you like */
  color: white;
}

.countdown {
  font-size: 7rem;
  font-weight: bold;
  letter-spacing: 0.2em;
  user-select: none;
  margin-bottom: 20px;
  /* space between countdown and h3 */
}

h3 {
  font-size: 1.5rem;
  text-align: center;
}