body {
    background: #2d2d2d;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100vh;
    color: #f6f6f6;
  }
  .timer {
    font-size: 5em;
    font-family: monospace;
  }
  .btn {
    font-size: 20px;
    padding: 10px 20px;
    margin: 0 15px;
  }