body {
  font-family: sans-serif;
  padding: 2em;
  max-width: 600px;
  margin: auto;
}

input {
  margin: 0.5em 0;
  padding: 0.5em;
  width: 100%;
}

button {
  margin-top: 1em;
  padding: 0.7em 1.2em;
  font-size: 1em;
}

.feedback {
  display: none;
  padding: 0.5em;
  margin-top: 1em;
  border-radius: 4px;
}
.feedback.info { background-color: #e0f7fa; color: #00796b; }
.feedback.success { background-color: #e8f5e9; color: #388e3c; }
.feedback.error { background-color: #ffebee; color: #d32f2f; }

.collapsible {
  display: none;
}
.collapsible.open {
  display: block;
}