body {
  background: linear-gradient(to bottom, #ffe6e6, #fff);
  font-family: 'Comic Sans MS', cursive;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
}

.carta {
  background-color: #fff;
  border: 2px solid #c0392b;
  padding: 2em;
  border-radius: 20px;
  box-shadow: 0 10px 25px rgba(0,0,0,0.2);
  text-align: center;
  max-width: 400px;
  animation: fadeIn 2s ease-in-out;
}

.carta h1 {
  color: #c0392b;
  margin-bottom: 1em;
}

.carta p {
  font-size: 1.1em;
  color: #444;
}

.heart-btn {
  margin-top: 1.5em;
  padding: 0.8em 1.5em;
  font-size: 1.1em;
  background-color: #ff4d6d;
  color: white;
  border: none;
  border-radius: 30px;
  cursor: pointer;
  animation: pulse 1.5s infinite;
  transition: background-color 0.3s ease;
}

.heart-btn:hover {
  background-color: #e60039;
}

@keyframes pulse {
  0% { transform: scale(1); }
  50% { transform: scale(1.1); }
  100% { transform: scale(1); }
}

#mensaje-extra {
  margin-top: 1.5em;
  font-size: 1.2em;
  color: #c0392b;
  display: none;
}

#mensaje-extra.hidden {
  display: none;
}

#mensaje-extra:not(.hidden) {
  display: block;
  animation: fadeIn 1s ease-in-out;
}

@keyframes fadeIn {
  from {opacity: 0; transform: translateY(10px);}
  to {opacity: 1; transform: translateY(0);}
}