/* ========================================
   CSS Variables & Reset
   ======================================== */
:root {
  --bg-color: #1a1f16;
  --bg-secondary: #232920;
  --text-color: #8b9a6b;
  --text-muted: #5a6648;
  --accent-color: #a4b87c;
  --accent-hover: #bdd192;
  --link-color: #8b9a6b;
  --link-hover: #a4b87c;
  --border-color: #3a4530;
  --card-bg: #232920;
  
  --font-mono: 'JetBrains Mono', monospace;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --spacing-2xl: 4rem;
  
  --max-width: 900px;
  --border-radius: 4px;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-mono);
  font-size: 14px;
  line-height: 1.7;
  color: var(--text-color);
  background-color: var(--bg-color);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ========================================
   Layout
   ======================================== */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--spacing-lg);
}

/* ========================================
   Header
   ======================================== */
.site-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-md) 0;
  margin-bottom: var(--spacing-xl);
  border-bottom: 1px solid var(--border-color);
}

.site-title {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--accent-color);
  text-decoration: none;
  letter-spacing: -0.02em;
}

.site-title:hover {
  color: var(--accent-hover);
}

.site-nav {
  display: flex;
  gap: var(--spacing-md);
}

.site-nav a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.875rem;
  transition: color 0.2s ease;
}

.site-nav a:hover {
  color: var(--accent-color);
}

/* ========================================
   Typography
   ======================================== */
h1, h2, h3, h4, h5, h6 {
  color: var(--accent-color);
  font-weight: 500;
  margin-bottom: var(--spacing-sm);
}

h2 {
  font-size: 1rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-top: var(--spacing-2xl);
  margin-bottom: var(--spacing-md);
}

p {
  margin-bottom: var(--spacing-sm);
}

a {
  color: var(--link-color);
  text-decoration: underline;
  text-underline-offset: 3px;
  transition: color 0.2s ease;
}

a:hover {
  color: var(--link-hover);
}

/* ========================================
   About Section
   ======================================== */
.about-section {
  margin-bottom: var(--spacing-2xl);
}

.section-label {
  color: var(--text-muted);
  font-size: 0.75rem;
  margin-bottom: var(--spacing-xs);
  font-style: italic;
}

.highlight-list {
  list-style: none;
  margin-bottom: var(--spacing-lg);
}

.highlight-list li {
  position: relative;
  padding-left: var(--spacing-md);
  margin-bottom: var(--spacing-xs);
}

.highlight-list li::before {
  content: "-";
  position: absolute;
  left: 0;
  color: var(--text-muted);
}

/* ========================================
   Tabs
   ======================================== */
.tabs-container {
  margin-top: var(--spacing-2xl);
}

.tab-nav {
  display: flex;
  gap: var(--spacing-lg);
  border-bottom: 2px solid var(--border-color);
  margin-bottom: var(--spacing-lg);
}

.tab-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: var(--spacing-sm) 0;
  cursor: pointer;
  position: relative;
  transition: color 0.2s ease;
}

.tab-btn:hover {
  color: var(--text-color);
}

.tab-btn.active {
  color: var(--accent-color);
}

.tab-btn.active::after {
  content: "";
  position: absolute;
  bottom: -2px;
  left: 0;
  right: 0;
  height: 2px;
  background-color: var(--accent-color);
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

/* ========================================
   Search & Filter
   ======================================== */
.search-container {
  margin-bottom: var(--spacing-md);
}

.search-input {
  width: 100%;
  padding: var(--spacing-sm);
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  color: var(--text-color);
  font-family: var(--font-mono);
  font-size: 0.875rem;
}

.search-input::placeholder {
  color: var(--text-muted);
}

.search-input:focus {
  outline: none;
  border-color: var(--accent-color);
}

.filter-container {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-lg);
  flex-wrap: wrap;
}

.filter-label {
  color: var(--text-muted);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.filter-btn {
  background: none;
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  padding: var(--spacing-xs) var(--spacing-sm);
  cursor: pointer;
  transition: all 0.2s ease;
}

.filter-btn:hover {
  border-color: var(--text-color);
  color: var(--text-color);
}

.filter-btn.active {
  background-color: var(--accent-color);
  border-color: var(--accent-color);
  color: var(--bg-color);
}

.book-count {
  margin-left: auto;
  color: var(--text-muted);
  font-size: 0.75rem;
}

/* ========================================
   Book Grid
   ======================================== */
.year-section {
  margin-bottom: var(--spacing-xl);
}

.year-label {
  color: var(--accent-color);
  font-size: 0.875rem;
  margin-bottom: var(--spacing-md);
  font-weight: 500;
}

.book-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
  gap: var(--spacing-md);
}

.book-card {
  position: relative;
  aspect-ratio: 2/3;
  border-radius: var(--border-radius);
  overflow: hidden;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.book-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.3);
}

.book-card img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.book-card .rating-badge {
  position: absolute;
  top: 6px;
  right: 6px;
  background-color: rgba(0, 0, 0, 0.7);
  color: var(--accent-color);
  font-size: 0.625rem;
  padding: 2px 6px;
  border-radius: 2px;
}

.book-placeholder {
  width: 100%;
  height: 100%;
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--border-color) 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--spacing-xs);
}

.book-placeholder span {
  font-size: 0.625rem;
  text-align: center;
  color: var(--text-muted);
  line-height: 1.3;
}

/* ========================================
   Projects Section
   ======================================== */
.projects-list {
  list-style: none;
}

.project-item {
  padding: var(--spacing-md) 0;
  border-bottom: 1px solid var(--border-color);
}

.project-item:last-child {
  border-bottom: none;
}

.project-title {
  color: var(--text-color);
  text-decoration: none;
  display: block;
  margin-bottom: var(--spacing-xs);
}

.project-title:hover {
  color: var(--accent-color);
}

.project-meta {
  color: var(--text-muted);
  font-size: 0.75rem;
}

/* ========================================
   Footer
   ======================================== */
.site-footer {
  margin-top: var(--spacing-2xl);
  padding-top: var(--spacing-lg);
  border-top: 1px solid var(--border-color);
  text-align: center;
}

.site-footer p {
  color: var(--text-muted);
  font-size: 0.875rem;
  margin-bottom: var(--spacing-sm);
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-md);
}

.footer-links a {
  color: var(--text-muted);
  font-size: 0.875rem;
}

.back-to-top {
  display: inline-block;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 1.25rem;
}

.back-to-top:hover {
  color: var(--accent-color);
}

/* ========================================
   Modal
   ======================================== */
.modal-overlay {
  position: fixed;
  inset: 0;
  background-color: rgba(0, 0, 0, 0.85);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s ease, visibility 0.3s ease;
}

.modal-overlay.active {
  opacity: 1;
  visibility: visible;
}

.modal-content {
  background-color: var(--bg-secondary);
  border-radius: var(--border-radius);
  padding: var(--spacing-lg);
  max-width: 400px;
  width: 90%;
  position: relative;
  transform: scale(0.95);
  transition: transform 0.3s ease;
}

.modal-overlay.active .modal-content {
  transform: scale(1);
}

.modal-close {
  position: absolute;
  top: var(--spacing-sm);
  right: var(--spacing-sm);
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 1.5rem;
  cursor: pointer;
  line-height: 1;
}

.modal-close:hover {
  color: var(--text-color);
}

.modal-book-cover {
  width: 120px;
  margin: 0 auto var(--spacing-md);
  display: block;
}

.modal-book-cover img {
  width: 100%;
  border-radius: var(--border-radius);
}

.modal-book-title {
  text-align: center;
  color: var(--accent-color);
  margin-bottom: var(--spacing-xs);
}

.modal-book-author {
  text-align: center;
  color: var(--text-muted);
  font-size: 0.875rem;
}

/* ========================================
   Responsive
   ======================================== */
@media (max-width: 640px) {
  .container {
    padding: var(--spacing-sm);
  }
  
  .site-header {
    flex-direction: column;
    gap: var(--spacing-sm);
    text-align: center;
  }
  
  .book-grid {
    grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
    gap: var(--spacing-sm);
  }
  
  .tab-nav {
    gap: var(--spacing-sm);
  }
  
  .filter-container {
    flex-direction: column;
    align-items: flex-start;
  }
  
  .book-count {
    margin-left: 0;
    margin-top: var(--spacing-sm);
  }
}