.glow-on-hover {
  width: 140px;
  height: 45px;
  border: none;
  outline: none;
  color: #fff;
  background: #111;
  cursor: pointer;
  position: relative;
  z-index: 0;
  border-radius: 10px;
  font-size: 14px;
  font-weight: bold;
  text-transform: uppercase;
}

.glow-on-hover:before {
  content: '';
  background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00,
    #00ffd5, #002bff, #7a00ff, #ff00c8, #ff0000);
  position: absolute;
  top: -2px;
  left: -2px;
  background-size: 400%;
  z-index: -1;
  filter: blur(4px);
  width: calc(100% + 4px);
  height: calc(100% + 4px);
  animation: glowing 20s linear infinite;
  opacity: 0;
  transition: opacity 0.3s ease-in-out;
  border-radius: 10px;
}

.glow-on-hover:hover:before {
  opacity: 1;
}

.glow-on-hover:after {
  content: '';
  background: #111;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border-radius: 10px;
  z-index: -1;
}

@keyframes glowing {
  0% { background-position: 0 0; }
  50% { background-position: 400% 0; }
  100% { background-position: 0 0; }
}

/* Responsivo */
@media (max-width: 768px) {
  .navbar {
    flex-wrap: wrap;
    gap: 8px;
  }

  .glow-on-hover {
    width: 100px;
    height: 40px;
    font-size: 12px;
  }
}