body {
  font-family: Arial, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
  background-color: #f0f0f0;
}

#app {
  text-align: center;
}

#timer {
  font-size: 48px;
  margin: 20px 0;
}

button {
  padding: 10px 20px;
  margin: 5px;
  font-size: 16px;
}