* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --bg-primary: #0a0a0a;
  --bg-secondary: #1a1a1a;
  --text-primary: #ffffff;
  --text-secondary: #aaaaaa;
  --accent: #ff6b6b;
  --spacing: 8px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
}

header {
  position: sticky;
  top: 0;
  background: var(--bg-secondary);
  padding: calc(var(--spacing) * 3) calc(var(--spacing) * 2);
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.5);
  z-index: 100;
}

h1 {
  font-size: 2rem;
  margin-bottom: calc(var(--spacing) * 2);
  text-align: center;
  background: linear-gradient(135deg, var(--accent), #ee5a6f);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

#gallery-nav {
  display: flex;
  gap: calc(var(--spacing) * 2);
  justify-content: center;
  flex-wrap: wrap;
}

.nav-btn {
  background: transparent;
  border: 2px solid var(--text-secondary);
  color: var(--text-secondary);
  padding: calc(var(--spacing) * 1.5) calc(var(--spacing) * 3);
  border-radius: 25px;
  cursor: pointer;
  transition: all 0.3s ease;
  font-size: 0.95rem;
  font-weight: 500;
}

.nav-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-2px);
}

.nav-btn.active {
  background: var(--accent);
  border-color: var(--accent);
  color: white;
}

.download-btn {
  background: linear-gradient(135deg, #667eea, #764ba2);
  border: none;
  color: white;
  padding: 12px 24px;
  border-radius: 25px;
  cursor: pointer;
  font-size: 1rem;
  font-weight: 600;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.download-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(102, 126, 234, 0.6);
}

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

.progress-bar {
  width: 300px;
  height: 8px;
  background: var(--bg-secondary);
  border-radius: 4px;
  overflow: hidden;
  margin: 0 auto;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, #667eea, #764ba2);
  width: 0%;
  transition: width 0.3s ease;
}

main {
  max-width: 1400px;
  margin: 0 auto;
  padding: calc(var(--spacing) * 4) calc(var(--spacing) * 2);
}

.photo-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: calc(var(--spacing) * 2);
  margin-bottom: calc(var(--spacing) * 4);
  grid-auto-flow: dense; /* Fill gaps with smaller items */
}

@media (max-width: 1024px) {
  .photo-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  /* Landscape photos span full width on tablet */
  .photo-item.landscape {
    grid-column: span 2;
  }
}

@media (max-width: 640px) {
  .photo-grid {
    grid-template-columns: 1fr;
  }

  /* All photos single column on mobile */
  .photo-item.landscape {
    grid-column: span 1;
  }

  h1 {
    font-size: 1.5rem;
  }
}

.photo-item {
  position: relative;
  overflow: hidden;
  border-radius: 8px;
  cursor: pointer;
  background: var(--bg-secondary);
  display: block;
}

.photo-item.landscape {
  grid-column: span 2;
}

.photo-item img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  transition: transform 0.3s ease, filter 0.3s ease;
  display: block;
}

.photo-item.landscape img {
  object-fit: cover;
  min-height: 300px;
}

.photo-item:hover img {
  transform: scale(1.05);
  filter: brightness(1.1);
}

.photo-item::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(to top, rgba(0, 0, 0, 0.7) 0%, transparent 50%);
  opacity: 0;
  transition: opacity 0.3s ease;
}

.photo-item:hover::after {
  opacity: 1;
}

.photo-info {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  padding: calc(var(--spacing) * 2);
  color: white;
  transform: translateY(100%);
  transition: transform 0.3s ease;
  z-index: 1;
}

.photo-item:hover .photo-info {
  transform: translateY(0);
}

.photo-info .gallery-name {
  font-size: 0.85rem;
  opacity: 0.9;
  font-weight: 500;
}

.loading {
  text-align: center;
  padding: calc(var(--spacing) * 4);
  color: var(--text-secondary);
  min-height: 100px; /* Ensure it's visible for intersection observer */
}

.spinner {
  border: 3px solid var(--bg-secondary);
  border-top: 3px solid var(--accent);
  border-radius: 50%;
  width: 40px;
  height: 40px;
  animation: spin 1s linear infinite;
  margin: 0 auto calc(var(--spacing) * 2);
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

.end-message {
  text-align: center;
  padding: calc(var(--spacing) * 4);
  color: var(--text-secondary);
  font-style: italic;
}

/* PhotoSwipe customization */
.pswp {
  --pswp-bg: #000000;
}

.pswp__img {
  object-fit: contain;
}