.certificate-lightbox {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.85);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transition: 0.3s;
  z-index: 9999;
}

.certificate-lightbox.active {
  opacity: 1;
  visibility: visible;
}

.certificate-lightbox img {
  max-width: 90%;
  max-height: 90%;
  border-radius: 12px;
  box-shadow: 0 0 40px rgba(0, 0, 0, 0.6);
  animation: zoomIn 0.35s ease;
}

@keyframes zoomIn {
  from {
    transform: scale(0.85);
    opacity: 0;
  }
  to {
    transform: scale(1);
    opacity: 1;
  }
}

.close-btn {
  position: absolute;
  top: 24px;
  right: 30px;
  font-size: 36px;
  color: #fff;
  cursor: pointer;
}

.nav-btn {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  background: rgba(255, 255, 255, 0.2);
  border: none;
  color: #fff;
  font-size: 26px;
  padding: 12px 18px;
  cursor: pointer;
  border-radius: 50%;
  transition: background 0.2s ease;
}

.nav-btn:hover {
  background: rgba(255, 255, 255, 0.35);
}

.prev {
  left: 25px;
}
.next {
  right: 25px;
}

@media (max-width: 576px) {
  .nav-btn {
    font-size: 22px;
    padding: 10px 14px;
  }
}