index.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-size: 62.5%;
}
.main {
  display: flex;
  flex-direction: column;
  margin-top: 5rem;
}

button {
  padding: 2.5rem;
  font-size: 2rem;
  margin: auto;
}