/* ============================================
   ENIHS ACADEMY - Category Page Styles
   Modern Expandable Category Interface
   ============================================ */

:root {
  --primary-color: #2563eb;
  --primary-dark: #1d4ed8;
  --primary-light: #3b82f6;
  --secondary-color: #f59e0b;
  --secondary-dark: #d97706;
  --accent-color: #10b981;
  --background-light: #f8fafc;
  --background-white: #ffffff;
  --text-dark: #1e293b;
  --text-medium: #475569;
  --text-light: #94a3b8;
  --border-color: #e2e8f0;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
  --header-bg: #1e293b;
  --nav-bg: #f59e0b;
  --footer-bg: #0f172a;
  --transition: all 0.3s ease;
  --border-radius: 12px;
}

html {
  transition: background-color 0.3s ease, color 0.3s ease;
}

button, a, .btn, .nav-link, .subject-link, .chapter-card, .video-card, .recent-card, .notice-item,
.feature-item, .book-cover-card, .class-btn, .sidebar-toggle-btn, .page-btn {
  transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease, transform 0.3s ease, box-shadow 0.3s ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  padding-top: 130px;
  background-color: var(--background-light);
  color: var(--text-dark);
  font-family:
    "DM Sans",
    -apple-system,
    BlinkMacSystemFont,
    "Segoe UI",
    Roboto,
    sans-serif;
  line-height: 1.6;
}

/* ============================================
   MAIN CONTENT LAYOUT
   ============================================ */

#main-content {
  flex: 1;
  width: 100%;
  max-width: 1400px;
  margin: 0 auto;
  padding: 24px 18px;
}

@media (min-width: 1200px) {
  #main-content {
    max-width: 1200px;
  }
}

.content-wrapper {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 22px;
  min-height: 600px;
}

.content-wrapper.reader-mode {
  grid-template-columns: 1fr;
}

/* ============================================
   SIDEBAR STYLES
   ============================================ */

.category-sidebar {
  position: sticky;
  top: 160px;
  height: calc(100vh - 190px);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  background: var(--background-white);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-md);
}

.category-sidebar.is-hidden {
  display: none;
}

.sidebar-toggle-btn {
  position: fixed;
  z-index: 1100;
  display: none;
  align-items: center;
  justify-content: center;
  background: var(--primary-color);
  color: #fff;
  border: none;
  box-shadow: 0 4px 14px rgba(37, 99, 235, 0.35);
  transition: var(--transition);
  bottom: 100px;
  right: 20px;
  width: 50px;
  height: 50px;
  border-radius: 50%;
  font-size: 20px;
  cursor: pointer;
}

.sidebar-overlay {
  position: fixed;
  inset: 0;
  z-index: 1099;
  display: none;
  background: rgba(15, 23, 42, 0.45);
  backdrop-filter: blur(2px);
}

.sidebar-overlay.active {
  display: block;
}

.sidebar-header {
  padding: 16px;
  color: white;
  background: linear-gradient(
    135deg,
    var(--primary-color),
    var(--primary-light)
  );
}

.sidebar-header h2 {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 18px;
  font-weight: 600;
}

.search-container {
  flex-shrink: 0;
  padding: 12px;
  border-bottom: 1px solid var(--border-color);
}

.search-box {
  display: flex;
  align-items: center;
  padding: 9px 12px;
  background: var(--background-light);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  transition: var(--transition);
}

.search-box:focus-within {
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.search-box i {
  margin-right: 10px;
  color: var(--text-light);
}

.search-box input {
  width: 100%;
  border: 0;
  outline: 0;
  background: transparent;
  color: var(--text-dark);
  font-size: 14px;
}

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

.class-accordion {
  flex: 1;
  overflow-x: hidden;
  overflow-y: auto;
  padding: 10px;
}

.class-item {
  margin-bottom: 8px;
}

.class-btn {
  display: flex;
  align-items: center;
  width: 100%;
  padding: 12px 14px;
  border: 0;
  border-radius: 8px;
  color: white;
  cursor: pointer;
  font-size: 15px;
  font-weight: 600;
  text-align: left;
  transition: var(--transition);
}

.class-btn[data-class="10"] {
  background: linear-gradient(135deg, #2563eb, #3b82f6);
}

.class-btn[data-class="11"] {
  background: linear-gradient(135deg, #059669, #10b981);
}

.class-btn[data-class="12"] {
  background: linear-gradient(135deg, #d97706, #f59e0b);
}

.class-btn:hover {
  transform: translateX(4px);
  box-shadow: var(--shadow-md);
}

.class-icon {
  width: 34px;
  height: 34px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  margin-right: 10px;
  background: rgba(255, 255, 255, 0.2);
  border-radius: 8px;
  font-size: 15px;
  font-weight: 700;
}

.class-name {
  flex: 1;
}

.toggle-icon {
  font-size: 12px;
  transition: transform 0.3s ease;
}

.class-btn.active .toggle-icon {
  transform: rotate(180deg);
}

.subject-list {
  max-height: 0;
  overflow: hidden;
  padding: 0 8px;
  transition:
    max-height 0.4s ease,
    padding 0.4s ease;
}

.subject-list.active {
  max-height: 1000px;
  padding: 12px 8px;
}

.subject-group {
  margin-bottom: 14px;
}

.subject-group:last-child {
  margin-bottom: 0;
}

.subject-group h4 {
  margin-bottom: 7px;
  padding-left: 5px;
  color: var(--text-light);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.5px;
  text-transform: uppercase;
}

.subject-link {
  display: flex;
  align-items: center;
  gap: 9px;
  margin-bottom: 4px;
  padding: 8px 12px;
  border-radius: 6px;
  color: var(--text-medium);
  font-size: 13px;
  text-decoration: none;
  transition: var(--transition);
}

.subject-link:hover,
.subject-link.active {
  background: var(--primary-color);
  color: white;
  transform: translateX(4px);
}

.subject-link i {
  width: 18px;
  font-size: 13px;
  text-align: center;
}

/* ============================================
   CONTENT AREA STYLES
   ============================================ */

.content-area {
  min-width: 0;
  max-width: 900px;
  margin: 0 auto;
  padding: 26px;
  background: var(--background-white);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-md);
}

.content-header {
  margin-bottom: 30px;
  padding-bottom: 20px;
  border-bottom: 2px solid var(--border-color);
}

.content-header h1 {
  margin-bottom: 5px;
  color: var(--text-dark);
  font-size: 28px;
  font-weight: 700;
}

.content-header p {
  color: var(--text-light);
  font-size: 14px;
}

.welcome-message {
  padding: 60px 36px;
  text-align: center;
  animation: fadeIn 0.5s ease;
}

.welcome-icon {
  width: 100px;
  height: 100px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 30px;
  background: linear-gradient(
    135deg,
    var(--primary-color),
    var(--primary-light)
  );
  border-radius: 50%;
}

.welcome-icon i {
  color: white;
  font-size: 45px;
}

.welcome-message h2 {
  margin-bottom: 15px;
  color: var(--text-dark);
  font-size: 28px;
  font-weight: 700;
}

.welcome-message p {
  max-width: 600px;
  margin: 0 auto 40px;
  color: var(--text-medium);
  font-size: 16px;
  line-height: 1.8;
}

.feature-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 18px;
  max-width: 600px;
  margin: 0 auto;
}
.feature-list a {
  text-decoration: none;
}
.feature-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
  padding: 18px;
  background: var(--background-light);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  transition: var(--transition);
}

.feature-item:hover {
  border-color: var(--primary-color);
  box-shadow: var(--shadow-md);
  transform: translateY(-4px);
}

.feature-item i {
  color: var(--primary-color);
  font-size: 28px;
}

.feature-item span {
  color: var(--text-dark);
  font-size: 13px;
  font-weight: 600;
}

.subject-content {
  display: none;
}

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

.chapter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
  margin-top: 20px;
}

.chapter-card {
  padding: 20px;
  background: var(--background-light);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: var(--transition);
}

.chapter-card:hover {
  border-color: var(--primary-color);
  box-shadow: var(--shadow-lg);
  transform: translateY(-5px);
}

.chapter-number {
  display: inline-block;
  width: 35px;
  height: 35px;
  margin-bottom: 12px;
  background: var(--primary-color);
  border-radius: 50%;
  color: white;
  font-size: 14px;
  font-weight: 600;
  line-height: 35px;
  text-align: center;
}

.chapter-title {
  margin-bottom: 8px;
  color: var(--text-dark);
  font-size: 16px;
  font-weight: 600;
}

.chapter-meta {
  display: flex;
  justify-content: space-between;
  color: var(--text-light);
  font-size: 12px;
}

/* ============================================
   BOOK SHELF
   ============================================ */

.book-shelf {
  padding: 10px;
}

.book-shelf-header {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 28px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--border-color);
}

.shelf-back-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
  padding: 8px 16px;
  background: var(--background-light);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  color: var(--text-dark);
  cursor: pointer;
  font-size: 13px;
  font-weight: 500;
  transition: var(--transition);
}

.shelf-back-btn:hover {
  border-color: var(--primary-color);
  color: var(--primary-color);
}

.shelf-title {
  flex: 1;
}

.shelf-badge {
  display: inline-block;
  margin-bottom: 4px;
  padding: 3px 10px;
  background: var(--primary-color);
  border-radius: 20px;
  color: white;
  font-size: 11px;
  font-weight: 600;
}

.shelf-badge.tag-10 {
  background: #2563eb;
}

.shelf-badge.tag-11 {
  background: #059669;
}

.shelf-badge.tag-12 {
  background: #d97706;
}

.shelf-title h2 {
  margin: 0;
  color: var(--text-dark);
  font-size: 22px;
  font-weight: 700;
}

.book-covers-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 22px;
  max-width: 800px;
  margin: 0 auto;
}

.book-cover-card {
  overflow: hidden;
  border: 1px solid var(--border-color);
  border-radius: 10px;
  box-shadow: var(--shadow-md);
  cursor: pointer;
  transition: var(--transition);
}

.book-cover-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-6px) scale(1.02);
}

.book-cover-art {
  position: relative;
  height: 190px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 12px;
  padding: 20px;
}

.book-cover-art i {
  color: white;
  font-size: 40px;
  opacity: 0.9;
}

.book-cover-art .cover-title {
  color: white;
  font-size: 14px;
  font-weight: 700;
  line-height: 1.4;
  text-align: center;
}

.book-cover-art .cover-ch-count {
  position: absolute;
  right: 10px;
  bottom: 8px;
  padding: 2px 8px;
  background: rgba(0, 0, 0, 0.2);
  border-radius: 20px;
  color: rgba(255, 255, 255, 0.8);
  font-size: 10px;
}

.book-cover-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 11px 14px;
  background: white;
}

.book-cover-footer span {
  color: var(--text-dark);
  font-size: 12px;
  font-weight: 600;
}

.read-now-btn {
  padding: 4px 12px;
  background: var(--primary-color);
  border: 0;
  border-radius: 6px;
  color: white;
  cursor: pointer;
  font-size: 11px;
  font-weight: 600;
  transition: var(--transition);
}

.read-now-btn:hover {
  background: var(--primary-dark);
}

.cover-physics {
  background: linear-gradient(135deg, #1e40af, #3b82f6);
}

.cover-chemistry {
  background: linear-gradient(135deg, #065f46, #10b981);
}

.cover-biology {
  background: linear-gradient(135deg, #6d28d9, #a78bfa);
}

.cover-math {
  background: linear-gradient(135deg, #92400e, #f59e0b);
}

.cover-nepali {
  background: linear-gradient(135deg, #9d174d, #f472b6);
}

.cover-english {
  background: linear-gradient(135deg, #0e7490, #22d3ee);
}

.cover-social {
  background: linear-gradient(135deg, #78350f, #d97706);
}

.cover-economics {
  background: linear-gradient(135deg, #1d4ed8, #60a5fa);
}

.cover-account {
  background: linear-gradient(135deg, #14532d, #4ade80);
}

.cover-optmath {
  background: linear-gradient(135deg, #7c2d12, #fb923c);
}

.cover-optcomputer {
  background: linear-gradient(135deg, #1e3a5f, #38bdf8);
}

.cover-business {
  background: linear-gradient(135deg, #4c1d95, #c084fc);
}

.cover-default {
  background: linear-gradient(135deg, #374151, #9ca3af);
}

/* ============================================
   BOOK READER
   ============================================ */

.book-reader {
  height: calc(100vh - 210px);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-md);
}

.reader-topbar {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-shrink: 0;
  padding: 11px 18px;
  background: linear-gradient(
    135deg,
    var(--primary-color),
    var(--primary-light)
  );
}

.reader-back-btn,
.reader-action-btn {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-shrink: 0;
  border-radius: 7px;
  color: white;
  cursor: pointer;
  font-size: 13px;
  transition: var(--transition);
  white-space: nowrap;
}

.reader-back-btn {
  padding: 7px 14px;
  background: rgba(255, 255, 255, 0.2);
  border: 1px solid rgba(255, 255, 255, 0.3);
  font-weight: 500;
}

.reader-action-btn {
  position: relative;
  padding: 7px 13px;
  background: rgba(255, 255, 255, 0.15);
  border: 1px solid rgba(255, 255, 255, 0.25);
}

.reader-back-btn:hover,
.reader-action-btn:hover {
  background: rgba(255, 255, 255, 0.32);
}

.reader-topbar-title {
  flex: 1;
  overflow: hidden;
  color: white;
  font-size: 15px;
  font-weight: 600;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.reader-topbar-actions {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

.soon-tag {
  position: absolute;
  top: -7px;
  right: -7px;
  padding: 1px 5px;
  background: #f59e0b;
  border-radius: 10px;
  color: white;
  font-size: 8px;
  font-weight: 700;
}

.buy-action-btn {
  background: rgba(255, 255, 255, 0.25);
  font-weight: 600;
}

.reader-body {
  display: flex;
  flex: 1;
  overflow: hidden;
}

.reader-nav {
  width: 220px;
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  background: var(--background-light);
  border-right: 1px solid var(--border-color);
  transition:
    width 0.3s ease,
    opacity 0.3s ease;
}

.reader-nav.nav-hidden {
  width: 0;
  opacity: 0;
  pointer-events: none;
}

.reader-nav-header {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
  padding: 13px 16px;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-light);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.5px;
  text-transform: uppercase;
}

.reader-nav-items {
  flex: 1;
  overflow-y: auto;
  padding: 8px;
}

.reader-nav-item {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 2px;
  padding: 10px 12px;
  border: 1px solid transparent;
  border-radius: 7px;
  color: var(--text-medium);
  cursor: pointer;
  font-size: 13px;
  transition: var(--transition);
}

.reader-nav-item:hover {
  background: white;
  border-color: var(--border-color);
  color: var(--text-dark);
}

.reader-nav-item.active {
  background: white;
  border-color: var(--primary-color);
  color: var(--primary-color);
  font-weight: 600;
}

.nav-num {
  width: 24px;
  height: 24px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  background: var(--border-color);
  border-radius: 5px;
  color: var(--text-dark);
  font-size: 11px;
  font-weight: 700;
}

.reader-nav-item.active .nav-num {
  background: var(--primary-color);
  color: white;
}

.reader-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  background: white;
}

.reader-content-inner {
  flex: 1;
  width: 100%;
  max-width: 820px;
  padding: 32px 38px;
  box-sizing: border-box;
}

.reader-content-inner h1 {
  margin-bottom: 10px;
  padding-bottom: 12px;
  border-bottom: 3px solid var(--primary-color);
  color: var(--text-dark);
  font-size: 26px;
  font-weight: 700;
}

.reader-content-inner h2 {
  margin: 26px 0 10px;
  color: var(--text-dark);
  font-size: 19px;
  font-weight: 600;
}

.reader-content-inner h3 {
  margin: 18px 0 8px;
  color: var(--primary-color);
  font-size: 15px;
  font-weight: 600;
}

.reader-content-inner p,
.reader-content-inner li {
  color: var(--text-medium);
  font-size: 15px;
  line-height: 1.85;
}

.reader-content-inner p {
  margin-bottom: 14px;
}

.reader-content-inner ul,
.reader-content-inner ol {
  margin-bottom: 16px;
  padding-left: 22px;
}

.reader-content-inner li {
  margin-bottom: 6px;
}

.note-box,
.warning-box {
  margin: 18px 0;
  padding: 13px 18px;
  border-radius: 0 8px 8px 0;
  color: var(--text-dark);
  font-size: 14px;
  line-height: 1.7;
}

.note-box {
  background: #eff6ff;
  border-left: 4px solid var(--primary-color);
}

.warning-box {
  background: #fffbeb;
  border-left: 4px solid #f59e0b;
}

.formula-box {
  margin: 16px 0;
  padding: 16px 20px;
  background: var(--background-light);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  color: var(--primary-color);
  font-family: "Courier New", monospace;
  font-size: 17px;
  font-weight: 700;
  letter-spacing: 0.5px;
  text-align: center;
}

.reader-content-inner table {
  width: 100%;
  overflow: hidden;
  margin: 16px 0;
  border-collapse: collapse;
  border-radius: 8px;
  font-size: 14px;
}

.reader-content-inner th {
  padding: 10px 14px;
  background: var(--primary-color);
  color: white;
  font-size: 13px;
  text-align: left;
}

.reader-content-inner td {
  padding: 10px 14px;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-medium);
}

.reader-content-inner tr:nth-child(even) td {
  background: var(--background-light);
}

.reader-pagination {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-shrink: 0;
  padding: 14px 38px;
  background: var(--background-light);
  border-top: 1px solid var(--border-color);
}

.page-btn {
  display: flex;
  align-items: center;
  gap: 7px;
  padding: 8px 18px;
  background: var(--primary-color);
  border: 0;
  border-radius: 8px;
  color: white;
  cursor: pointer;
  font-size: 13px;
  font-weight: 500;
  transition: var(--transition);
}

.page-btn:hover {
  background: var(--primary-dark);
}

.page-btn:disabled {
  background: var(--border-color);
  color: var(--text-light);
  cursor: not-allowed;
}

#page-indicator {
  color: var(--text-light);
  font-size: 13px;
  font-weight: 500;
}

/* ============================================
   RESPONSIVE STYLES
   ============================================ */

@media (max-width: 1024px) {
  .content-wrapper {
    grid-template-columns: 260px 1fr;
  }

  .feature-list {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  body {
    padding-top: 85px;
  }

  #main-content {
    padding: 18px 14px;
  }

  .content-wrapper {
    grid-template-columns: 1fr;
  }

  .category-sidebar {
    position: fixed;
    top: var(--header-h, 130px);
    left: 0;
    z-index: 1100;
    width: min(300px, 85vw);
    height: calc(100vh - var(--header-h, 130px));
    max-height: none;
    transform: translateX(-110%);
    transition: transform 0.3s ease;
  }

  .category-sidebar.open {
    transform: translateX(0);
  }

  .sidebar-toggle-btn {
    display: flex;
  }

  .content-area {
    padding: 18px;
  }

  .welcome-message {
    padding: 40px 18px;
  }

  .feature-list {
    grid-template-columns: 1fr 1fr;
  }

  .book-reader {
    height: calc(100vh - 160px);
  }

  .reader-body {
    position: relative;
  }

  .reader-nav {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    z-index: 30;
    width: min(82vw, 300px);
    display: flex;
    border-right: 1px solid var(--border-color);
    box-shadow: var(--shadow-lg);
    transform: translateX(0);
    opacity: 1;
  }

  .reader-nav.nav-hidden {
    width: min(82vw, 300px);
    opacity: 1;
    pointer-events: none;
    transform: translateX(-105%);
  }

  #toggle-nav-btn {
    position: fixed;
    right: 18px;
    bottom: 78px;
    z-index: 60;
    min-width: 120px;
    justify-content: center;
    padding: 11px 14px;
    background: var(--primary-color);
    border-color: var(--primary-dark);
    box-shadow: var(--shadow-lg);
  }

  #toggle-nav-btn::after {
    content: "Chapters";
    font-size: 13px;
    font-weight: 700;
  }

  #toggle-nav-btn:hover {
    background: var(--primary-dark);
  }

  .reader-content-inner {
    padding: 20px 16px;
  }

  .reader-topbar {
    flex-wrap: wrap;
  }

  .reader-topbar-title {
    display: none;
  }

  .reader-topbar-actions {
    flex: 1;
    justify-content: flex-end;
  }

  .book-covers-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 14px;
  }

  .reader-pagination {
    padding: 12px 16px;
  }
}

@media (max-width: 480px) {
  .content-area {
    padding: 16px;
  }

  .content-header h1 {
    font-size: 22px;
  }

  .welcome-message h2 {
    font-size: 23px;
  }

  .feature-list {
    grid-template-columns: 1fr;
  }

  .class-btn {
    padding: 11px 13px;
    font-size: 14px;
  }

  .book-shelf-header {
    align-items: flex-start;
    flex-direction: column;
  }

  .book-covers-grid {
    grid-template-columns: 1fr;
  }

  .book-cover-art {
    height: 210px;
  }

  .reader-action-btn span:not(.soon-tag),
  .buy-action-btn {
    font-size: 12px;
  }

  .reader-pagination {
    gap: 10px;
  }

  .page-btn {
    padding: 8px 12px;
  }
}

/* ============================================
   ANIMATION
   ============================================ */

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(20px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ============================================
   DARK MODE
   ============================================ */
[data-theme="dark"] {
  --primary-color: #3b82f6;
  --primary-dark: #2563eb;
  --primary-light: #60a5fa;
  --secondary-color: #f59e0b;
  --secondary-dark: #d97706;
  --accent-color: #10b981;
  --background-light: #0f1117;
  --background-white: #1a1d27;
  --surface-raised: #21253a;
  --surface-hover: #272b40;
  --text-dark: #e8eaf0;
  --text-medium: #9da5b4;
  --text-light: #636b7a;
  --border-color: #2a2f45;
  --header-bg: #0d1117;
  --nav-bg: #1a1d27;
  --footer-bg: #0a0d14;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.5);
  --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.6);
}

[data-theme="dark"] body {
  background: #0f1117 !important;
  color: #e8eaf0;
}

[data-theme="dark"] .category-sidebar,
[data-theme="dark"] .content-area,
[data-theme="dark"] .chapter-card,
[data-theme="dark"] .feature-item,
[data-theme="dark"] .book-cover-footer,
[data-theme="dark"] .reader-content,
[data-theme="dark"] .reader-nav-item:hover,
[data-theme="dark"] .reader-nav-item.active {
  background: #1a1d27;
  border-color: #2a2f45;
  color: #e8eaf0;
}

[data-theme="dark"] .reader-nav-item:hover,
[data-theme="dark"] .reader-nav-item.active {
  color: #60a5fa;
}

[data-theme="dark"] .reader-nav-item.active {
  border-color: #3b82f6;
}

[data-theme="dark"] .search-box input {
  color: #e8eaf0;
}

[data-theme="dark"] .subject-link {
  color: #9da5b4;
}

[data-theme="dark"] .subject-link:hover,
[data-theme="dark"] .subject-link.active {
  color: #fff;
}

[data-theme="dark"] h1,
[data-theme="dark"] h2,
[data-theme="dark"] h3,
[data-theme="dark"] h4,
[data-theme="dark"] .chapter-title,
[data-theme="dark"] .content-header h1 {
  color: #e8eaf0;
}

[data-theme="dark"] p,
[data-theme="dark"] .chapter-meta,
[data-theme="dark"] .content-header p {
  color: #9da5b4;
}

[data-theme="dark"] #main-nav {
  background-color: #1a1d27;
  border-bottom: 1px solid #2a2f45;
}

[data-theme="dark"] .nav-link {
  color: #c9cdd6;
}

[data-theme="dark"] .nav-link:hover,
[data-theme="dark"] .nav-link.active {
  background: rgba(59, 130, 246, 0.15);
  color: #60a5fa;
}

[data-theme="dark"] input,
[data-theme="dark"] select,
[data-theme="dark"] textarea {
  background: #21253a;
  color: #e8eaf0;
  border-color: #2a2f45;
}

[data-theme="dark"] input::placeholder {
  color: #636b7a;
}

[data-theme="dark"] .katex,
[data-theme="dark"] .math-block,
[data-theme="dark"] .content-body,
[data-theme="dark"] .reader-content-inner {
  color: #e8eaf0;
}

[data-theme="dark"] .reader-content-inner p,
[data-theme="dark"] .reader-content-inner li {
  color: #9da5b4;
}

[data-theme="dark"] .note-box {
  background: #1e2a3a;
  color: #e8eaf0;
}

[data-theme="dark"] .warning-box {
  background: #2a2418;
  color: #e8eaf0;
}

[data-theme="dark"] pre,
[data-theme="dark"] code {
  background: #0d1117;
  color: #c9d1d9;
  border-color: #2a2f45;
}

[data-theme="dark"] table {
  color: #e8eaf0;
}
[data-theme="dark"] th {
  background: #21253a;
  color: #e8eaf0;
  border-color: #2a2f45;
}
[data-theme="dark"] td {
  border-color: #2a2f45;
}
[data-theme="dark"] tr:nth-child(even) {
  background: #1e2230;
}

[data-theme="dark"] .sidebar,
[data-theme="dark"] #sidebar {
  background: #1a1d27;
  border-color: #2a2f45;
}

[data-theme="dark"] ::-webkit-scrollbar {
  width: 8px;
}
[data-theme="dark"] ::-webkit-scrollbar-track {
  background: #0f1117;
}
[data-theme="dark"] ::-webkit-scrollbar-thumb {
  background: #2a2f45;
  border-radius: 4px;
}
[data-theme="dark"] ::-webkit-scrollbar-thumb:hover {
  background: #3b82f6;
}