body {
  margin: 0;
  font-family: system-ui, sans-serif;
  background: #111;
  color: #fff;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.viewer {
  position: relative;
  max-width: 90vw;
  max-height: 85vh;
  margin-top: 20px;
}

.viewer img {
  max-width: 100%;
  max-height: 85vh;
  border-radius: 8px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.6);
}

.nav {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  background: rgba(0,0,0,0.6);
  color: #fff;
  border: none;
  font-size: 2rem;
  padding: 10px 14px;
  cursor: pointer;
  border-radius: 50%;
  z-index: 10;
  pointer-events: auto;
}

.prev { left: -10px; }
.next { right: -10px; }

.counter {
  margin: 12px 0 20px;
  font-size: 0.9rem;
  opacity: 0.8;
}
.back-container {
  margin-top: 20px;
  display: flex;
  justify-content: center;
}

.back-btn {
  background: #333;
  color: #fff;
  text-decoration: none;
  padding: 10px 20px;
  border-radius: 5px;
  font-size: 0.9rem;
  transition: background 0.3s;
  border: 1px solid #444;
}

.back-btn:hover {
  background: #444;
}
/* Mobile tweaks */
@media (max-width: 600px) {
  .nav {
    font-size: 1.6rem;
    padding: 8px 12px;
  }
}