.menu {
  max-height: 0;
  overflow: hidden;
  background: linear-gradient(to right, #39C2C7, #0D55A0); /* Degradê de duas cores */
  padding: 0;
  border: 0px solid #ccc;
  transition: max-height 0.5s ease, padding 0.5s ease;
}
.menu.open {
  max-height: 1000px; /* Valor suficiente para acomodar o conteúdo */
  padding: 10px;
animation: borderBlink 1s ease, backgroundGradient 10s linear infinite;
}
@keyframes borderBlink {
  0%, 100% {
      border-color: #ccc;
  }
  50% {
      border-color: #ff0000;
  }
}
@keyframes backgroundGradient {
  0% {
      background-position: 0% 50%;
  }
  50% {
      background-position: 100% 50%;
  }
  100% {
      background-position: 0% 50%;
  }
}
.menu {
  background: linear-gradient(to right, #39C2C7, #0D55A0);
  background-size: 200% 200%;
}