/* ==========================================================================
   IIT Madras BS Degree — MLT Week-wise Question Portal
   Strict 2-3 Professional Academic Palette:
   - Surface: Pure White (#ffffff) & Subtle Off-White (#f8fafc)
   - Slate Navy / Text: #0f172a, #334155, #64748b
   - Academic Blue Accent: #2563eb, #1d4ed8
   - Borders: #e2e8f0
   ========================================================================== */

:root {
  --bg-main: #ffffff;
  --bg-subtle: #f8fafc;
  --bg-card: #ffffff;
  --border-color: #e2e8f0;
  --border-hover: #cbd5e1;
  
  --text-primary: #0f172a;
  --text-secondary: #334155;
  --text-muted: #64748b;
  
  --accent-blue: #2563eb;
  --accent-blue-hover: #1d4ed8;
  --accent-blue-light: #eff6ff;
  
  --sidebar-width: 220px;
  --rail-width: 48px;
  --header-height: 56px;
  --pdf-toolbar-height: 42px;
  --transition-speed: 0.22s;
  --transition-curve: cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background-color: var(--bg-main);
  color: var(--text-primary);
  min-height: 100vh;
  overflow-x: hidden;
  display: flex;
  flex-direction: column;
}

/* ==========================================================================
   Top Header (Shown in Central Overview; Hidden when PDF is Active)
   ========================================================================== */
.top-header {
  height: var(--header-height);
  background-color: #ffffff;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 24px;
  z-index: 50;
  flex-shrink: 0;
}

/* Reclaim vertical screen space: when PDF is open, hide main top header */
body.pdf-active .top-header {
  display: none !important;
}

.brand-section {
  display: flex;
  align-items: center;
  gap: 12px;
}

.brand-badge {
  background-color: var(--text-primary);
  color: #ffffff;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.8px;
  padding: 4px 8px;
  border-radius: 4px;
  text-transform: uppercase;
}

.brand-title {
  font-size: 16px;
  font-weight: 600;
  color: var(--text-primary);
  letter-spacing: -0.2px;
}

.brand-title span {
  color: var(--accent-blue);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 10px;
}

.btn-minimal {
  background-color: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
  padding: 5px 12px;
  font-size: 13px;
  font-weight: 500;
  border-radius: 6px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: all 0.15s ease;
}

.btn-minimal:hover {
  background-color: var(--bg-subtle);
  border-color: var(--border-hover);
  color: var(--text-primary);
}

.btn-primary {
  background-color: var(--accent-blue);
  color: #ffffff;
  border: 1px solid var(--accent-blue);
  padding: 5px 12px;
  font-size: 13px;
  font-weight: 500;
  border-radius: 6px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: all 0.15s ease;
}

.btn-primary:hover {
  background-color: var(--accent-blue-hover);
}

.student-tag {
  font-size: 12px;
  color: var(--text-muted);
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  background-color: var(--bg-subtle);
  padding: 4px 10px;
  border-radius: 4px;
  border: 1px solid var(--border-color);
}

/* ==========================================================================
   Main Application Viewport
   ========================================================================== */
.app-viewport {
  flex: 1;
  position: relative;
  overflow: visible;
  display: flex;
  background-color: #ffffff;
}

/* ==========================================================================
   Mode 1: Central Gallery View
   ========================================================================== */
.center-gallery-view {
  width: 100%;
  min-height: calc(100vh - var(--header-height));
  overflow: visible;
  padding: 32px 24px 80px;
  display: flex;
  flex-direction: column;
  align-items: center;
  transition: opacity var(--transition-speed) var(--transition-curve);
}

.gallery-container {
  width: 100%;
  max-width: 1140px;
}

.gallery-header {
  text-align: center;
  margin-bottom: 38px;
}

.gallery-eyebrow {
  font-size: 13px;
  font-weight: 700;
  color: var(--accent-blue);
  letter-spacing: 1.2px;
  text-transform: uppercase;
  margin-bottom: 10px;
}

.gallery-title {
  font-size: 32px;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 8px;
  letter-spacing: -0.5px;
}

.gallery-subtitle {
  font-size: 14.5px;
  color: var(--text-muted);
  max-width: 620px;
  margin: 0 auto;
  line-height: 1.5;
}

/* 6 Left, 6 Right List Layout on Desktop - Expanded Width & Height */
.weeks-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  grid-template-rows: repeat(6, auto);
  grid-auto-flow: column;
  gap: 16px 28px;
  max-width: 1060px;
  margin: 0 auto;
}

.week-card {
  background-color: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 18px 24px;
  cursor: pointer;
  display: flex;
  flex-direction: row;
  justify-content: space-between;
  align-items: center;
  transition: all 0.18s ease;
  min-height: 64px;
}

.week-card:hover {
  border-color: var(--accent-blue);
  background-color: #f8faff;
  box-shadow: 0 4px 16px rgba(37, 99, 235, 0.09);
  transform: translateY(-1px);
}

.week-card-left {
  display: flex;
  align-items: center;
  gap: 16px;
}

.week-index {
  font-size: 12.5px;
  font-weight: 700;
  color: var(--accent-blue);
  background-color: var(--accent-blue-light);
  padding: 5px 10px;
  border-radius: 6px;
  letter-spacing: 0.5px;
  min-width: 32px;
  text-align: center;
}

.week-label {
  font-size: 17px;
  font-weight: 600;
  color: var(--text-primary);
  letter-spacing: -0.3px;
  transition: color 0.15s ease;
}

.week-card:hover .week-label {
  color: var(--accent-blue);
}

.week-card-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

.card-format-tag {
  font-size: 11.5px;
  font-weight: 600;
  color: var(--text-muted);
  background-color: var(--bg-subtle);
  border: 1px solid var(--border-color);
  padding: 3px 8px;
  border-radius: 5px;
  letter-spacing: 0.5px;
}

.week-open-arrow {
  color: var(--text-muted);
  display: inline-flex;
  align-items: center;
  transition: all 0.18s ease;
}

.week-open-arrow svg {
  width: 17px;
  height: 17px;
}

.week-card:hover .week-open-arrow {
  color: var(--accent-blue);
  transform: translateX(3px);
}

/* Footer & Disclaimer */
.gallery-footer {
  border-top: 1px solid var(--border-color);
  padding-top: 24px;
  margin-top: 32px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.footer-profile-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
}

.footer-author-badge {
  font-size: 12.5px;
  font-weight: 600;
  color: var(--text-secondary);
  background-color: var(--bg-subtle);
  border: 1px solid var(--border-color);
  padding: 6px 14px;
  border-radius: 6px;
}

.footer-social-links {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.footer-social-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  font-weight: 500;
  color: var(--text-secondary);
  text-decoration: none;
  background-color: #ffffff;
  border: 1px solid var(--border-color);
  padding: 6px 12px;
  border-radius: 6px;
  transition: all 0.15s ease;
}

.footer-social-btn:hover {
  border-color: var(--accent-blue);
  color: var(--accent-blue);
  background-color: var(--accent-blue-light);
}

.footer-disclaimer-text {
  font-size: 11.5px;
  color: var(--text-muted);
  line-height: 1.5;
  background-color: var(--bg-subtle);
  border: 1px solid var(--border-color);
  padding: 8px 14px;
  border-radius: 6px;
  text-align: center;
}

.footer-disclaimer-text strong {
  color: var(--text-secondary);
}

/* ==========================================================================
   Gallery Hero (Full viewport so footer is reached via scroll)
   ========================================================================== */
.gallery-hero {
  min-height: calc(100vh - var(--header-height) - 80px);
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 10px 0 20px;
}

/* ==========================================================================
   Footer Scholar Hub Bar (Theme Blue / Slate Palette, No Green)
   ========================================================================== */
.footer-scholar-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
  background-color: var(--bg-subtle);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 11px 16px;
  text-decoration: none;
  cursor: pointer;
  transition: all 0.18s ease;
}

.footer-scholar-bar:hover {
  border-color: var(--accent-blue);
  background-color: #f8faff;
  box-shadow: 0 4px 14px rgba(37, 99, 235, 0.08);
  transform: translateY(-1px);
}

.footer-scholar-left {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.footer-scholar-brand {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 12.5px;
  font-weight: 600;
  color: var(--accent-blue);
  transition: color 0.15s ease;
}

.footer-scholar-bar:hover .footer-scholar-brand {
  color: var(--accent-blue-hover);
}

.footer-scholar-desc {
  font-size: 11.5px;
  color: var(--text-muted);
  transition: color 0.15s ease;
}

.footer-scholar-bar:hover .footer-scholar-desc {
  color: var(--text-secondary);
}

.footer-scholar-square-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  background-color: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  color: var(--text-muted);
  transition: all 0.18s ease;
  flex-shrink: 0;
}

.footer-scholar-bar:hover .footer-scholar-square-btn {
  border-color: var(--accent-blue);
  color: var(--accent-blue);
  background-color: var(--accent-blue-light);
  transform: translate(1px, -1px);
}

/* ==========================================================================
   Mode 2: Split View Mode (Slide to Left, PDF to Right)
   ========================================================================== */
.split-view {
  width: 100%;
  height: 100vh;
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  z-index: 100;
}

.app-viewport.state-split .center-gallery-view {
  display: none;
}

.app-viewport.state-split .split-view {
  display: flex;
}

/* ==========================================================================
   Left Drawer / Sidebar
   ========================================================================== */
.left-drawer {
  width: var(--sidebar-width);
  height: 100%;
  background-color: #ffffff;
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  position: relative;
  z-index: 20;
  transition: width var(--transition-speed) var(--transition-curve);
  flex-shrink: 0;
}

.drawer-header {
  padding: 0 12px;
  height: var(--pdf-toolbar-height);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  background-color: var(--bg-subtle);
  flex-shrink: 0;
}

.drawer-header-title {
  font-size: 13px;
  font-weight: 700;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 6px;
}

.drawer-header-actions {
  display: flex;
  align-items: center;
  gap: 6px;
}

.btn-icon {
  background: #ffffff;
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  width: 28px;
  height: 28px;
  border-radius: 4px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: all 0.15s ease;
}

.btn-icon:hover {
  background-color: #ffffff;
  border-color: var(--border-hover);
  color: var(--text-primary);
}

.drawer-content {
  flex: 1;
  overflow-y: auto;
  padding: 10px;
}

.drawer-weeks-list {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.week-nav-btn {
  width: 100%;
  text-align: left;
  background-color: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 9px 12px;
  font-size: 13px;
  font-weight: 600;
  color: var(--text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  transition: all 0.15s ease;
}

.week-nav-btn:hover {
  border-color: var(--accent-blue);
  color: var(--accent-blue);
  background-color: var(--accent-blue-light);
}

.week-nav-btn.active {
  background-color: var(--accent-blue);
  color: #ffffff;
  border-color: var(--accent-blue);
}

.week-nav-btn.active .week-nav-arrow {
  color: #ffffff;
}

.week-nav-arrow {
  font-size: 12px;
  color: var(--text-muted);
}

/* ==========================================================================
   Collapsed State (Slim 5-space rail)
   ========================================================================== */
.left-drawer.collapsed {
  width: var(--rail-width);
}

.left-drawer.collapsed .drawer-header,
.left-drawer.collapsed .drawer-content {
  display: none !important;
}

.collapsed-rail-items {
  display: none;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  padding-top: 8px;
  height: 100%;
}

.left-drawer.collapsed .collapsed-rail-items {
  display: flex;
}

.rail-btn {
  width: 34px;
  height: 34px;
  border-radius: 6px;
  border: 1px solid var(--border-color);
  background-color: var(--bg-subtle);
  color: var(--text-secondary);
  font-size: 11.5px;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.15s ease;
}

.rail-btn:hover {
  background-color: #ffffff;
  border-color: var(--accent-blue);
  color: var(--accent-blue);
}

.rail-btn.active {
  background-color: var(--accent-blue);
  color: #ffffff;
  border-color: var(--accent-blue);
}

.rail-divider {
  width: 22px;
  height: 1px;
  background-color: var(--border-color);
  margin: 3px 0;
}

/* ==========================================================================
   Right PDF Viewer Stage (Slim 42px Toolbar, PDF Flush to Top)
   ========================================================================== */
.right-stage {
  flex: 1;
  height: 100%;
  display: flex;
  flex-direction: column;
  background-color: #f1f5f9;
  position: relative;
  overflow: hidden;
}

.pdf-toolbar {
  height: var(--pdf-toolbar-height);
  background-color: #ffffff;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 14px;
  z-index: 10;
  flex-shrink: 0;
}

.pdf-info {
  display: flex;
  align-items: center;
  gap: 10px;
}

.pdf-current-title {
  font-size: 14px;
  font-weight: 700;
  color: var(--text-primary);
  margin-left: 2px;
}

.pdf-controls {
  display: flex;
  align-items: center;
  gap: 6px;
}

.pdf-toolbar .btn-minimal,
.pdf-toolbar .btn-primary {
  padding: 4px 9px;
  font-size: 12px;
  height: 28px;
}

.pdf-toolbar .student-tag {
  padding: 3px 8px;
  font-size: 11px;
  height: 28px;
  display: inline-flex;
  align-items: center;
}

.pdf-container {
  flex: 1;
  width: 100%;
  height: calc(100% - var(--pdf-toolbar-height));
  position: relative;
  background-color: #525659;
}

.pdf-frame {
  width: 100%;
  height: 100%;
  border: none;
  display: block;
}

/* ==========================================================================
   Responsive Adaptations (Multi-Device)
   ========================================================================== */
@media (max-width: 1024px) {
  .weeks-grid {
    max-width: 800px;
    gap: 10px 18px;
  }
}

@media (max-width: 768px) {
  :root {
    --sidebar-width: 180px;
    --rail-width: 42px;
    --header-height: 50px;
    --pdf-toolbar-height: 40px;
  }

  .top-header {
    padding: 0 14px;
  }

  .brand-title {
    font-size: 14px;
  }

  .student-tag,
  .pdf-toolbar .student-tag {
    display: none !important;
  }

  .weeks-grid {
    grid-template-columns: 1fr;
    grid-template-rows: none;
    grid-auto-flow: row;
    gap: 10px;
    max-width: 100%;
  }

  .week-card {
    padding: 12px 16px;
  }

  .pdf-toolbar {
    padding: 0 8px;
  }

  .pdf-controls .btn-minimal span,
  .pdf-controls .btn-primary span {
    display: none;
  }

  .pdf-controls .btn-minimal,
  .pdf-controls .btn-primary {
    padding: 4px 6px;
  }

  /* Drawer on mobile: floats over content when opened, hidden when collapsed */
  .left-drawer:not(.collapsed) {
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    width: 200px;
    z-index: 40;
    box-shadow: 2px 0 16px rgba(0,0,0,0.15);
  }

  .left-drawer.collapsed {
    position: relative;
    box-shadow: none;
  }
}

@media (max-width: 480px) {
  .center-gallery-view {
    padding: 20px 14px 40px;
  }

  .gallery-title {
    font-size: 20px;
  }

  .gallery-subtitle {
    font-size: 13px;
  }

  .weeks-grid {
    grid-template-columns: 1fr;
    grid-template-rows: none;
    grid-auto-flow: row;
    gap: 8px;
  }

  .week-card {
    padding: 11px 14px;
    min-height: auto;
  }

  .week-label {
    font-size: 14.5px;
  }

  .footer-social-links {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    width: 100%;
  }

  .footer-social-btn {
    padding: 6px 4px;
    font-size: 11px;
    justify-content: center;
  }

  .footer-scholar-bar {
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
    gap: 10px;
    padding: 10px 12px;
  }

  .pdf-info .btn-minimal span {
    display: none;
  }
}

/* Searchable study guides share the portal's typography and color palette. */
a.week-card { color: inherit; text-decoration: none; }
a:focus-visible, button:focus-visible { outline: 3px solid var(--accent-blue); outline-offset: 4px; }
.study-section { max-width: 1060px; margin: 32px auto; line-height: 1.7; }
.study-section h2 { font-size: 22px; letter-spacing: -.3px; margin-bottom: 14px; }
.study-section h3 { font-size: 17px; margin-bottom: 8px; }
.study-section p { color: var(--text-secondary); margin-bottom: 14px; }
.study-section a, .breadcrumbs a, .week-pagination a { color: var(--accent-blue); text-underline-offset: 3px; }
.week-page { width: 100%; max-width: 1060px; margin: 0 auto; padding: 32px 24px 48px; }
.week-page .gallery-header { text-align: left; margin: 26px 0; }
.week-page .gallery-subtitle { max-width: 800px; margin: 0; }
.week-page .study-section { margin: 28px 0; }
.breadcrumbs { color: var(--text-muted); font-size: 14px; }
.resource-meta { margin-top: 16px; color: var(--text-secondary); font-size: 14px; }
.resource-actions { display: flex; flex-wrap: wrap; gap: 12px; margin: 20px 0; }
.resource-actions a, a.btn-minimal { text-decoration: none; }
.revision-list { padding-left: 24px; }
.revision-list li { padding: 5px 0; color: var(--text-secondary); }
.week-pagination { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 16px; padding: 20px 0; border-top: 1px solid var(--border-color); }
.skip-link { position: absolute; left: 16px; top: -80px; padding: 12px; background: white; z-index: 100; }
.skip-link:focus { top: 8px; }
@media (max-width: 768px) {
  .week-page { padding: 24px 18px 36px; }
  .study-section h2 { font-size: 20px; }
  .week-page .gallery-title { font-size: 26px; }
}
.resource-actions a.btn-primary { color: #ffffff; }