body {
  display: flex;
  justify-content: center;
  align-items: center;
  margin: 0;
  padding: 16px;
}

.contenedor {
  background: white;
  padding: 50px;
  border-radius: 20px;
  max-width: 600px;
  width: 100%;
  text-align: center;
}

h1 {
  text-decoration: underline;
  margin-bottom: 30px;
  margin-top: 0;
}

.display {
  font-size: 80px;
  font-weight: bold;
  color: #1e3c72;
  background-color: #c3cfe2;
  padding: 40px;
  border-radius: 15px;
  margin-bottom: 40px;
  letter-spacing: 8px;
}

.controles {
  display: flex;
  justify-content: center;
  gap: 15px;
  flex-wrap: wrap;
}

.btn {
  padding: 15px 30px;
  font-size: 18px;
  font-weight: bold;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  transition: all 0.3s;
  color: white;
  min-width: 140px;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none !important;
}

.btn-iniciar {
  background-color: #667eea;
}

.btn-pausar {
  background-color: #f5576c;
}

.btn-reiniciar {
  background-color: #00f2fe;
}

.volver {
  display: inline-block;
  margin-top: 30px;
  padding: 12px 25px;
  background-color: #1e3c72;
  text-decoration: none;
  color: white;
  border-radius: 10px;
  font-weight: bold;
}