/* ==========================================================================
   Study Notes - Modern & Clean Design System
   Palettes: Light background, Vibrant Ocean Blue & Teal Accents
   ========================================================================== */

:root {
  /* Color Palette */
  --primary-50: #eff6ff;
  --primary-100: #dbeafe;
  --primary-500: #2563eb;
  --primary-600: #1d4ed8;
  --primary-700: #1e40af;
  
  --teal-50: #f0fdfa;
  --teal-100: #ccfbf1;
  --teal-500: #0d9488;
  --teal-600: #0f766e;
  --teal-700: #115e59;

  --accent-gradient: linear-gradient(135deg, #1d4ed8 0%, #0d9488 100%);
  --accent-gradient-hover: linear-gradient(135deg, #1e40af 0%, #0f766e 100%);

  /* Neutrals */
  --bg-page: #f8fafc;
  --bg-card: #ffffff;
  --bg-card-subtle: #f1f5f9;
  
  --text-main: #0f172a;
  --text-muted: #64748b;
  --text-light: #94a3b8;
  --border-color: #e2e8f0;
  --border-focus: #3b82f6;

  /* States */
  --success-bg: #ecfdf5;
  --success-border: #a7f3d0;
  --success-text: #065f46;

  --error-bg: #fef2f2;
  --error-border: #fecaca;
  --error-text: #991b1b;

  --warning-bg: #fffbeb;
  --warning-border: #fde68a;
  --warning-text: #92400e;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.07), 0 2px 4px -2px rgb(0 0 0 / 0.05);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.08), 0 4px 6px -4px rgb(0 0 0 / 0.05);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.05);

  /* Radius */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 20px;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-normal: 250ms ease;
}

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

html, body {
  min-height: 100%;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background-color: var(--bg-page);
  color: var(--text-main);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* Global Container */
.container {
  width: 100%;
  max-width: 1140px;
  margin-left: auto;
  margin-right: auto;
  padding-left: 20px;
  padding-right: 20px;
}

/* Header & Navigation */
.navbar {
  background-color: #ffffff;
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 40;
  backdrop-filter: blur(8px);
}

.navbar-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 68px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: var(--text-main);
}

.brand-icon {
  width: 40px;
  height: 40px;
  background: var(--accent-gradient);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  box-shadow: 0 4px 10px rgba(37, 99, 235, 0.25);
}

.brand-icon svg {
  width: 22px;
  height: 22px;
  stroke: currentColor;
}

.brand-text {
  display: flex;
  flex-direction: column;
}

.brand-title {
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.brand-subtitle {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-weight: 500;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 16px;
}

.nav-link {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-muted);
  text-decoration: none;
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.nav-link:hover {
  color: var(--primary-600);
  background-color: var(--primary-50);
}

.nav-badge {
  background-color: var(--teal-50);
  color: var(--teal-700);
  border: 1px solid var(--teal-100);
  font-size: 0.75rem;
  font-weight: 600;
  padding: 4px 10px;
  border-radius: var(--radius-full);
}

/* Hero Section */
.hero-section {
  padding: 48px 0 32px 0;
  text-align: center;
}

.hero-pill {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--primary-50);
  color: var(--primary-700);
  border: 1px solid var(--primary-100);
  font-size: 0.825rem;
  font-weight: 600;
  padding: 6px 14px;
  border-radius: var(--radius-full);
  margin-bottom: 16px;
}

.hero-title {
  font-size: 2.5rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  color: var(--text-main);
  margin-bottom: 12px;
  line-height: 1.2;
}

.hero-description {
  font-size: 1.1rem;
  color: var(--text-muted);
  max-width: 640px;
  margin: 0 auto 28px auto;
}

/* Search & Filter Bar */
.search-wrapper {
  max-width: 520px;
  margin: 0 auto;
  position: relative;
}

.search-icon {
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-light);
  pointer-events: none;
}

.search-input {
  width: 100%;
  padding: 13px 18px 13px 44px;
  font-size: 0.95rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-full);
  background: #ffffff;
  color: var(--text-main);
  outline: none;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-fast);
}

.search-input:focus {
  border-color: var(--primary-500);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

/* Alert Banners */
.alert-banner {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 14px 18px;
  border-radius: var(--radius-md);
  margin-bottom: 24px;
  font-size: 0.925rem;
}

.alert-banner.warning {
  background: var(--warning-bg);
  border: 1px solid var(--warning-border);
  color: var(--warning-text);
}

.alert-banner.info {
  background: var(--primary-50);
  border: 1px solid var(--primary-100);
  color: var(--primary-700);
}

.alert-banner.error {
  background: var(--error-bg);
  border: 1px solid var(--error-border);
  color: var(--error-text);
}

.alert-banner.success {
  background: var(--success-bg);
  border: 1px solid var(--success-border);
  color: var(--success-text);
}

/* Chapter Card Section */
.chapters-section {
  padding-bottom: 60px;
}

.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
}

.section-title {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-main);
}

.chapter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 24px;
}

.chapter-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 28px;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  transition: transform var(--transition-normal), box-shadow var(--transition-normal), border-color var(--transition-normal);
  position: relative;
  overflow: hidden;
}

.chapter-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 4px;
  background: var(--accent-gradient);
}

.chapter-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: #cbd5e1;
}

.chapter-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 12px;
}

.chapter-badge {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 4px 10px;
  background: var(--primary-50);
  color: var(--primary-700);
  border-radius: var(--radius-full);
}

.chapter-tag {
  font-size: 0.75rem;
  font-weight: 600;
  padding: 4px 10px;
  background: var(--teal-50);
  color: var(--teal-700);
  border-radius: var(--radius-full);
}

.chapter-title {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--text-main);
  line-height: 1.3;
  margin-bottom: 10px;
}

.chapter-description {
  font-size: 0.95rem;
  color: var(--text-muted);
  line-height: 1.6;
  margin-bottom: 20px;
  flex-grow: 1;
}

.chapter-features {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 24px;
}

.feature-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.8rem;
  color: var(--text-muted);
  background: var(--bg-card-subtle);
  padding: 4px 10px;
  border-radius: var(--radius-sm);
}

.feature-pill svg {
  width: 14px;
  height: 14px;
  stroke: var(--teal-600);
}

.card-footer {
  margin-top: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 18px;
  border-top: 1px solid var(--border-color);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-size: 0.925rem;
  font-weight: 600;
  padding: 10px 20px;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  text-decoration: none;
  transition: all var(--transition-fast);
}

.btn-primary {
  background: var(--accent-gradient);
  color: #ffffff;
  box-shadow: 0 2px 6px rgba(37, 99, 235, 0.25);
}

.btn-primary:hover {
  background: var(--accent-gradient-hover);
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.35);
  transform: translateY(-1px);
}

.btn-secondary {
  background: #ffffff;
  color: var(--text-main);
  border: 1px solid var(--border-color);
}

.btn-secondary:hover {
  background: var(--bg-card-subtle);
  border-color: #cbd5e1;
}

.btn-sm {
  padding: 6px 12px;
  font-size: 0.825rem;
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none !important;
}

.filter-tab.active {
  background: var(--accent-gradient);
  color: #ffffff;
  border-color: transparent;
}

/* ==========================================================================
   Full Screen / Embedded Reader Overlay
   ========================================================================== */
#reader-view {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background: #ffffff;
  z-index: 100;
  flex-direction: column;
}

#reader-view.active {
  display: flex;
}

.reader-header {
  height: 60px;
  background: #ffffff;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 20px;
  box-shadow: var(--shadow-sm);
  z-index: 10;
}

.reader-title-group {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
}

.reader-title {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-main);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.reader-controls {
  display: flex;
  align-items: center;
  gap: 10px;
}

.reader-iframe-container {
  flex: 1;
  width: 100%;
  height: calc(100vh - 60px);
  position: relative;
  background: #f8fafc;
}

.reader-iframe {
  width: 100%;
  height: 100%;
  border: none;
  background: #ffffff;
}

/* Loading & Error States inside Reader */
.state-overlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 24px;
  text-align: center;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(4px);
  z-index: 20;
}

.spinner {
  width: 44px;
  height: 44px;
  border: 4px solid var(--primary-100);
  border-top-color: var(--primary-600);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  margin-bottom: 16px;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.state-title {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 8px;
}

.state-desc {
  font-size: 0.95rem;
  color: var(--text-muted);
  max-width: 440px;
  margin-bottom: 20px;
}

/* ==========================================================================
   Admin Dashboard Styles
   ========================================================================== */
.admin-page {
  padding: 40px 0 80px 0;
}

.admin-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 32px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--border-color);
}

.admin-user-info {
  display: flex;
  align-items: center;
  gap: 14px;
}

.user-avatar {
  width: 42px;
  height: 42px;
  border-radius: var(--radius-full);
  background: var(--teal-100);
  color: var(--teal-700);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1rem;
}

.user-email {
  font-weight: 600;
  color: var(--text-main);
  font-size: 0.95rem;
}

.user-role {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* Auth Card */
.auth-card-container {
  max-width: 440px;
  margin: 40px auto;
}

.auth-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  padding: 36px 32px;
  box-shadow: var(--shadow-lg);
}

.auth-header {
  text-align: center;
  margin-bottom: 28px;
}

.auth-title {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--text-main);
  margin-bottom: 6px;
}

.auth-subtitle {
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* Forms */
.form-group {
  margin-bottom: 20px;
}

.form-label {
  display: block;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-main);
  margin-bottom: 8px;
}

.form-input {
  width: 100%;
  padding: 11px 14px;
  font-size: 0.95rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background: #ffffff;
  color: var(--text-main);
  outline: none;
  transition: all var(--transition-fast);
}

.form-input:focus {
  border-color: var(--primary-500);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

/* Upload Panel */
.upload-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 32px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 30px;
}

.upload-card-header {
  margin-bottom: 24px;
}

.upload-card-title {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 4px;
}

.upload-card-desc {
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* Dropzone */
.dropzone {
  border: 2px dashed var(--border-color);
  border-radius: var(--radius-lg);
  padding: 40px 20px;
  text-align: center;
  background: var(--bg-card-subtle);
  cursor: pointer;
  transition: all var(--transition-fast);
  margin-bottom: 20px;
}

.dropzone:hover, .dropzone.dragover {
  border-color: var(--primary-500);
  background: var(--primary-50);
}

.dropzone-icon {
  width: 48px;
  height: 48px;
  margin: 0 auto 12px auto;
  color: var(--primary-600);
}

.dropzone-title {
  font-weight: 600;
  color: var(--text-main);
  margin-bottom: 4px;
}

.dropzone-hint {
  font-size: 0.825rem;
  color: var(--text-muted);
}

/* File Selected Info Pill */
.file-preview-pill {
  display: none;
  align-items: center;
  justify-content: space-between;
  background: var(--teal-50);
  border: 1px solid var(--teal-100);
  padding: 12px 18px;
  border-radius: var(--radius-md);
  margin-bottom: 20px;
}

.file-preview-pill.active {
  display: flex;
}

.file-preview-info {
  display: flex;
  align-items: center;
  gap: 12px;
}

.file-preview-name {
  font-weight: 600;
  color: var(--teal-700);
  font-size: 0.925rem;
}

.file-preview-size {
  font-size: 0.8rem;
  color: var(--teal-600);
}

/* Upload Progress Bar */
.progress-container {
  display: none;
  margin-bottom: 20px;
}

.progress-container.active {
  display: block;
}

.progress-bar-bg {
  width: 100%;
  height: 8px;
  background: var(--border-color);
  border-radius: var(--radius-full);
  overflow: hidden;
  margin-bottom: 8px;
}

.progress-bar-fill {
  width: 0%;
  height: 100%;
  background: var(--accent-gradient);
  transition: width 0.3s ease;
}

.progress-status {
  display: flex;
  justify-content: space-between;
  font-size: 0.825rem;
  color: var(--text-muted);
}

/* Storage Target Card */
.info-box {
  background: var(--bg-card-subtle);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 18px;
  font-size: 0.875rem;
  margin-bottom: 24px;
}

.info-row {
  display: flex;
  justify-content: space-between;
  padding: 6px 0;
}

.info-row:not(:last-child) {
  border-bottom: 1px dashed var(--border-color);
}

.info-label {
  color: var(--text-muted);
  font-weight: 500;
}

.info-value {
  color: var(--text-main);
  font-family: monospace;
  font-weight: 600;
}

/* Footer */
.footer {
  margin-top: auto;
  border-top: 1px solid var(--border-color);
  padding: 24px 0;
  background: #ffffff;
  font-size: 0.875rem;
  color: var(--text-muted);
  text-align: center;
}

/* Responsiveness */
@media (max-width: 768px) {
  .hero-title {
    font-size: 2rem;
  }
  
  .chapter-grid {
    grid-template-columns: 1fr;
  }

  .admin-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 16px;
  }

  .navbar-inner {
    height: auto;
    padding-top: 12px;
    padding-bottom: 12px;
  }
}