button[type="submit"] {
  display: inline-block;
}

button[type="submit"] + #spinner:not([hidden]) {
  display: inline-block;
  vertical-align: middle;
  margin-left: 0.75rem;
}

#spinner {
  width: 1.5rem;
  height: 1.5rem;
  border: 3px solid #ccc;
  border-top-color: #333;
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

#output {
    margin-top: 2rem;
    padding: 20px;
    background-color: #eee;
}

#output h2 {
    margin-top: 0;
}