style.css

h1 {
  text-align: center;
  display: block;
}

#swap-btn {
  flex: 0 0 auto !important;
  width: fit-content !important;
  min-width: unset !important;
  align-self: center;
}

#swap-btn button {
  width: 2.5rem;
  height: 2.5rem;
  min-width: unset;
  padding: 0;
  font-size: 1.25rem;
  border-radius: 50%;
}