body {
  background: #0f172a;
  color: white;
  font-family: Arial;
}

.pagina {
  max-width: 900px;
  margin: 0 auto;
  padding: 20px;
}

.zona {
  border: 2px dashed #22c55e;
  padding: 20px;
  margin: 20px;
  min-height: 120px;
  transition: 0.3s;
}

.zona.activa {
  background: rgba(34,197,94,0.2);
}

.item {
  background: #1f2937;
  padding: 20px;
  margin: 10px;
  cursor: grab;
  font-size: 30px;
}

.item.arrastrando {
  opacity: 0.5;
}

button {
  margin: 20px;
}