/* ==========================================================================
   Anthropic Certifications Theory Study Portal - Modern Stylesheet
   Theme: Slate / Emerald / Indigo with Full Dark/Light Mode Support
   ========================================================================== */

/* --- 1. Variables & Design Tokens --- */
:root,
[data-theme="light"] {
  --color-bg-app: #f8fafc;
  --color-bg-header: rgba(255, 255, 255, 0.85);
  --color-bg-surface: #ffffff;
  --color-bg-card: #ffffff;
  --color-bg-hover: #f1f5f9;
  --color-bg-active: #e2e8f0;
  --color-bg-subtle: #f8fafc;
  
  --color-border: #e2e8f0;
  --color-border-subtle: #edf2f7;
  --color-border-focus: #6366f1;

  --color-text-main: #0f172a;
  --color-text-secondary: #475569;
  --color-text-muted: #94a3b8;
  --color-text-inverse: #ffffff;

  --color-primary: #4f46e5;
  --color-primary-light: #e0e7ff;
  --color-primary-dark: #3730a3;
  --color-primary-glow: rgba(79, 70, 229, 0.15);

  --color-accent-emerald: #059669;
  --color-accent-emerald-light: #d1fae5;
  --color-accent-amber: #d97706;
  --color-accent-amber-light: #fef3c7;

  --color-code-bg: #0f172a;
  --color-code-header: #1e293b;
  --color-code-text: #f1f5f9;
  --color-code-border: #334155;

  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-modal: 0 20px 25px -5px rgba(0, 0, 0, 0.15), 0 10px 10px -5px rgba(0, 0, 0, 0.04);

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-full: 9999px;

  --header-height: 64px;
  --sidebar-width: 320px;
}

[data-theme="dark"] {
  --color-bg-app: #090d16;
  --color-bg-header: rgba(15, 23, 42, 0.85);
  --color-bg-surface: #0f172a;
  --color-bg-card: #131d33;
  --color-bg-hover: #1e293b;
  --color-bg-active: #27354f;
  --color-bg-subtle: #0f172a;

  --color-border: #1e293b;
  --color-border-subtle: #172033;
  --color-border-focus: #818cf8;

  --color-text-main: #f8fafc;
  --color-text-secondary: #cbd5e1;
  --color-text-muted: #64748b;
  --color-text-inverse: #0f172a;

  --color-primary: #818cf8;
  --color-primary-light: #1e1b4b;
  --color-primary-dark: #a5b4fc;
  --color-primary-glow: rgba(129, 140, 248, 0.2);

  --color-accent-emerald: #34d399;
  --color-accent-emerald-light: #064e3b;
  --color-accent-amber: #fbbf24;
  --color-accent-amber-light: #78350f;

  --color-code-bg: #060a12;
  --color-code-header: #0f172a;
  --color-code-text: #e2e8f0;
  --color-code-border: #1e293b;

  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -1px rgba(0, 0, 0, 0.2);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5), 0 4px 6px -2px rgba(0, 0, 0, 0.3);
  --shadow-modal: 0 25px 50px -12px rgba(0, 0, 0, 0.7);
}

/* --- 2. Base & Reset --- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 15px;
  line-height: 1.6;
  scroll-behavior: smooth;
  color: var(--color-text-main);
  background-color: var(--color-bg-app);
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
  max-width: 100vw;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
  max-width: 100vw;
  width: 100%;
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color 0.15s ease;
}

a:hover {
  text-decoration: underline;
}

button {
  font-family: inherit;
  font-size: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

kbd {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.75rem;
  padding: 0.15rem 0.35rem;
  border-radius: 4px;
  background: var(--color-bg-active);
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
}

/* --- 3. App Layout --- */
.app-layout {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  width: 100%;
  max-width: 100vw;
  overflow-x: hidden;
  min-width: 0;
}

/* --- 4. Top Header --- */
.top-header {
  position: sticky;
  top: 0;
  z-index: 40;
  height: var(--header-height);
  background: var(--color-bg-header);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
  gap: 1rem;
}

.header-left, .header-right {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.brand-logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none !important;
  color: var(--color-text-main);
}

.logo-icon {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, #4f46e5 0%, #059669 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #ffffff;
  box-shadow: 0 4px 10px var(--color-primary-glow);
}

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

.brand-title {
  font-weight: 700;
  font-size: 1rem;
  letter-spacing: -0.01em;
  color: var(--color-text-main);
  line-height: 1.2;
}

.brand-badge {
  font-size: 0.72rem;
  color: var(--color-text-muted);
  font-weight: 500;
}

/* Cert Navigation Tabs */
.cert-nav-tabs {
  display: flex;
  align-items: center;
  background: var(--color-bg-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 3px;
  margin-left: 1rem;
}

.cert-tab-btn {
  padding: 0.35rem 0.85rem;
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  border-radius: var(--radius-sm);
  transition: all 0.15s ease;
}

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

.cert-tab-btn.active {
  background: var(--color-primary);
  color: #ffffff;
  font-weight: 600;
  box-shadow: var(--shadow-sm);
}

/* Search Trigger Bar */
.search-trigger-btn {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  background: var(--color-bg-surface);
  border: 1px solid var(--color-border);
  padding: 0.45rem 0.9rem;
  border-radius: var(--radius-md);
  color: var(--color-text-muted);
  font-size: 0.85rem;
  min-width: 240px;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.search-trigger-btn:hover {
  border-color: var(--color-border-focus);
  color: var(--color-text-secondary);
}

.search-placeholder {
  flex: 1;
  text-align: left;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.search-kbd {
  font-size: 0.75rem;
  padding: 0.1rem 0.4rem;
  border-radius: 4px;
}

/* Progress Indicator Widget */
.progress-widget {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  background: var(--color-bg-surface);
  border: 1px solid var(--color-border);
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-md);
}

.progress-info {
  display: flex;
  flex-direction: column;
}

.progress-label {
  font-size: 0.65rem;
  text-transform: uppercase;
  color: var(--color-text-muted);
  font-weight: 600;
  letter-spacing: 0.05em;
  line-height: 1;
}

.progress-percent {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--color-accent-emerald);
}

.progress-bar-container {
  width: 70px;
  height: 6px;
  background: var(--color-bg-active);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent-emerald));
  border-radius: var(--radius-full);
  transition: width 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.progress-count {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  white-space: nowrap;
}

/* Icon Buttons */
.icon-btn {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  background: var(--color-bg-surface);
  color: var(--color-text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.15s ease;
}

.icon-btn:hover {
  background: var(--color-bg-hover);
  color: var(--color-text-main);
  border-color: var(--color-border-focus);
}

/* Dark/Light toggle logic in CSS */
[data-theme="light"] .moon-icon {
  display: block;
}
[data-theme="light"] .sun-icon {
  display: none;
}
[data-theme="dark"] .moon-icon {
  display: none;
}
[data-theme="dark"] .sun-icon {
  display: block;
}

.mobile-only {
  display: none;
}

/* --- 5. Workspace Container --- */
.workspace-container {
  display: flex;
  flex: 1;
  position: relative;
  min-height: calc(100vh - var(--header-height));
  min-width: 0;
  width: 100%;
  max-width: 100vw;
  overflow-x: hidden;
}

/* --- 6. Sidebar --- */
.sidebar {
  width: var(--sidebar-width);
  min-width: var(--sidebar-width);
  background: var(--color-bg-surface);
  border-right: 1px solid var(--color-border);
  display: flex;
  flex-direction: column;
  height: calc(100vh - var(--header-height));
  position: sticky;
  top: var(--header-height);
  overflow: hidden;
  z-index: 20;
  transition: width 0.25s cubic-bezier(0.4, 0, 0.2, 1),
              min-width 0.25s cubic-bezier(0.4, 0, 0.2, 1),
              margin-left 0.25s cubic-bezier(0.4, 0, 0.2, 1),
              opacity 0.2s ease,
              visibility 0.25s ease;
}

/* Desktop Collapsed Sidebar State */
@media (min-width: 1025px) {
  .app-layout.sidebar-collapsed .sidebar {
    width: 0 !important;
    min-width: 0 !important;
    margin-left: calc(-1 * var(--sidebar-width)) !important;
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    border-right-color: transparent;
  }

  .app-layout.sidebar-collapsed .reading-area {
    max-width: 1100px;
  }
}

.sidebar-header {
  padding: 1rem 1.25rem;
  border-bottom: 1px solid var(--color-border);
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.sidebar-header-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.sidebar-title {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: 700;
  color: var(--color-text-muted);
}

.sidebar-close-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: var(--radius-sm);
  color: var(--color-text-muted);
  cursor: pointer;
  transition: all 0.15s ease;
}

.sidebar-close-btn:hover {
  color: var(--color-text-main);
  background: var(--color-bg-subtle);
  border-color: var(--color-border-focus);
}

.cert-select {
  width: 100%;
  padding: 0.45rem 0.65rem;
  border-radius: var(--radius-sm);
  background: var(--color-bg-app);
  color: var(--color-text-main);
  border: 1px solid var(--color-border);
  font-size: 0.82rem;
  outline: none;
  cursor: pointer;
}

.cert-select:focus {
  border-color: var(--color-border-focus);
}

.sidebar-curriculum {
  flex: 1;
  overflow-y: auto;
  padding: 0.75rem 0.5rem;
}

.sidebar-loading, .sidebar-empty {
  padding: 1.5rem 1rem;
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.85rem;
}

/* Curriculum Group & Items */
.cert-group {
  margin-bottom: 1.25rem;
}

.cert-group-header {
  padding: 0.4rem 0.75rem;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--color-primary);
  letter-spacing: 0.05em;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.cert-group-count {
  font-size: 0.7rem;
  color: var(--color-text-muted);
  font-weight: 500;
}

/* Module / Domain Accordion */
.module-group {
  margin-bottom: 0.5rem;
}

.module-header-btn {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  padding: 0.45rem 0.65rem;
  background: var(--color-bg-subtle, rgba(255, 255, 255, 0.03));
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  color: var(--color-text-main);
  cursor: pointer;
  text-align: left;
  transition: background 0.15s ease, border-color 0.15s ease;
}

.module-header-btn:hover {
  background: var(--color-bg-hover);
  border-color: var(--color-border-focus);
}

.module-header-title-wrap {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  min-width: 0;
  flex: 1;
}

.module-chevron {
  flex-shrink: 0;
  color: var(--color-text-muted);
  transition: transform 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.module-group.collapsed .module-chevron {
  transform: rotate(-90deg);
}

.module-group.collapsed .module-lesson-list {
  display: none;
}

.module-header-title {
  font-size: 0.78rem;
  font-weight: 600;
  line-height: 1.3;
  color: var(--color-text-main);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.module-header-count {
  font-size: 0.7rem;
  color: var(--color-text-muted);
  font-weight: 600;
  flex-shrink: 0;
  background: var(--color-bg-surface);
  padding: 2px 6px;
  border-radius: 9999px;
  border: 1px solid var(--color-border);
}

.module-lesson-list {
  margin-top: 0.25rem;
  padding-left: 0.25rem;
  border-left: 2px solid var(--color-border);
  margin-left: 0.5rem;
}

.lesson-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.lesson-item {
  display: flex;
  align-items: flex-start;
  gap: 0.65rem;
  padding: 0.55rem 0.75rem;
  border-radius: var(--radius-sm);
  text-decoration: none;
  color: var(--color-text-secondary);
  transition: all 0.15s ease;
  position: relative;
  cursor: pointer;
}

.lesson-item:hover {
  background: var(--color-bg-hover);
  color: var(--color-text-main);
  text-decoration: none;
}

.lesson-item.active {
  background: var(--color-primary-light);
  color: var(--color-primary);
  font-weight: 600;
}

.lesson-item.completed .lesson-title {
  color: var(--color-text-muted);
}

/* Lesson Checkbox Touch-Friendly */
.lesson-checkbox-wrap {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 44px;
  min-height: 44px;
  padding: 6px;
  margin: -6px 2px -6px -8px;
  cursor: pointer;
  border-radius: var(--radius-sm);
  transition: background 0.15s ease;
}

.lesson-checkbox-wrap:hover {
  background: rgba(255, 255, 255, 0.05);
}

.lesson-checkbox {
  appearance: none;
  -webkit-appearance: none;
  width: 18px;
  height: 18px;
  border: 1.5px solid var(--color-border);
  border-radius: 5px;
  cursor: pointer;
  background: var(--color-bg-surface);
  position: relative;
  transition: all 0.15s ease;
  flex-shrink: 0;
}

.lesson-checkbox:checked {
  background: var(--color-accent-emerald);
  border-color: var(--color-accent-emerald);
}

.lesson-checkbox:checked::after {
  content: "";
  position: absolute;
  left: 5px;
  top: 2px;
  width: 5px;
  height: 9px;
  border: solid #ffffff;
  border-width: 0 2px 2px 0;
  transform: rotate(45deg);
}

.lesson-info {
  flex: 1;
  min-width: 0;
}

.lesson-header-row {
  display: flex;
  align-items: baseline;
  gap: 0.4rem;
}

.lesson-number {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.75rem;
  color: var(--color-text-muted);
  font-weight: 600;
}

.lesson-title {
  font-size: 0.85rem;
  line-height: 1.35;
  white-space: normal;
}

.lesson-meta-row {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  margin-top: 0.25rem;
  flex-wrap: wrap;
}

.lesson-read-time {
  font-size: 0.7rem;
  color: var(--color-text-muted);
  display: inline-flex;
  align-items: center;
  gap: 0.2rem;
}

/* Tag Badges */
.tag-badge {
  font-size: 0.68rem;
  padding: 0.1rem 0.45rem;
  border-radius: var(--radius-full);
  background: var(--color-bg-active);
  color: var(--color-text-secondary);
  font-weight: 500;
  white-space: nowrap;
}

.tag-badge.emerald {
  background: var(--color-accent-emerald-light);
  color: var(--color-accent-emerald);
}

.tag-badge.indigo {
  background: var(--color-primary-light);
  color: var(--color-primary);
}

/* --- 7. Reading Area --- */
.reading-area {
  flex: 1;
  overflow-y: auto;
  overflow-x: hidden;
  padding: 2.5rem 3rem 5rem;
  max-width: 1000px;
  margin: 0 auto;
  width: 100%;
  min-width: 0;
  box-sizing: border-box;
  transition: max-width 0.25s ease;
}

.content-wrapper {
  display: flex;
  flex-direction: column;
  gap: 1.75rem;
  width: 100%;
  min-width: 0;
  box-sizing: border-box;
  overflow-wrap: break-word;
  word-break: break-word;
}

/* Breadcrumbs */
.breadcrumbs {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.82rem;
  color: var(--color-text-muted);
  flex-wrap: wrap;
  overflow: hidden;
}

.breadcrumb-separator {
  opacity: 0.6;
}

.breadcrumb-active {
  color: var(--color-text-main);
  font-weight: 500;
}

.breadcrumb-module {
  color: var(--color-primary);
  font-weight: 500;
}

/* Lesson Header Badges */
.lesson-header-badges {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
}

.module-badge {
  display: inline-flex;
  align-items: center;
  padding: 0.25rem 0.65rem;
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  font-weight: 600;
  background: var(--color-primary-light);
  color: var(--color-primary);
  border: 1px solid var(--color-primary);
}

.lesson-num-badge {
  display: inline-flex;
  align-items: center;
  padding: 0.25rem 0.6rem;
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  font-weight: 700;
  background: var(--color-bg-surface);
  color: var(--color-text-main);
  border: 1px solid var(--color-border);
}

.subdomain-badge {
  display: inline-flex;
  align-items: center;
  padding: 0.25rem 0.65rem;
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  font-weight: 500;
  background: rgba(59, 130, 246, 0.1);
  color: #3b82f6;
  border: 1px solid rgba(59, 130, 246, 0.25);
  max-width: 100%;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

/* Lesson Header Card */
.lesson-page-header {
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 1.25rem;
}

.lesson-main-title {
  font-size: 2.1rem;
  font-weight: 800;
  letter-spacing: -0.025em;
  color: var(--color-text-main);
  line-height: 1.2;
  margin-bottom: 0.75rem;
}

.lesson-header-meta {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}

/* Key Concept Callout Card */
.key-concept-card {
  position: relative;
  background: linear-gradient(145deg, var(--color-bg-card) 0%, var(--color-bg-subtle) 100%);
  border: 1px solid var(--color-border);
  border-left: 4px solid var(--color-primary);
  border-radius: var(--radius-md);
  padding: 1.35rem 1.5rem;
  box-shadow: var(--shadow-sm);
}

.key-concept-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-primary);
  margin-bottom: 0.5rem;
}

.key-concept-text {
  font-size: 1.05rem;
  font-weight: 500;
  line-height: 1.6;
  color: var(--color-text-main);
}

/* Section styling */
.lesson-section {
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
}

.lesson-section-heading {
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--color-text-main);
  letter-spacing: -0.01em;
  margin-top: 0.5rem;
  border-bottom: 1px solid var(--color-border-subtle);
  padding-bottom: 0.35rem;
}

.lesson-section-content {
  font-size: 0.98rem;
  line-height: 1.75;
  color: var(--color-text-secondary);
}

.lesson-section-content p {
  margin-bottom: 0.85rem;
}

.lesson-section-content ul, .lesson-section-content ol {
  margin-left: 1.5rem;
  margin-bottom: 0.85rem;
}

.lesson-section-content li {
  margin-bottom: 0.35rem;
}

/* Code Blocks & Copy Button */
.code-block-wrapper {
  margin: 1.25rem 0;
  border-radius: var(--radius-md);
  overflow: hidden;
  border: 1px solid var(--color-code-border);
  background: var(--color-code-bg);
  box-shadow: var(--shadow-md);
}

.code-block-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.45rem 1rem;
  background: var(--color-code-header);
  border-bottom: 1px solid var(--color-code-border);
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.75rem;
  color: var(--color-text-muted);
}

.copy-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.72rem;
  padding: 0.25rem 0.6rem;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.08);
  color: #cbd5e1;
  border: 1px solid rgba(255, 255, 255, 0.1);
  transition: all 0.15s ease;
}

.copy-btn:hover {
  background: rgba(255, 255, 255, 0.18);
  color: #ffffff;
}

.copy-btn.copied {
  background: var(--color-accent-emerald);
  color: #ffffff;
  border-color: var(--color-accent-emerald);
}

.code-pre {
  margin: 0;
  padding: 1.15rem 1.25rem;
  overflow-x: auto;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.88rem;
  line-height: 1.6;
  color: var(--color-code-text);
  background: transparent;
}

/* Inline code */
:not(pre) > code {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.85em;
  padding: 0.15em 0.4em;
  background: var(--color-bg-active);
  color: var(--color-primary);
  border-radius: 4px;
}

/* Key Takeaways Card */
.takeaways-card {
  background: linear-gradient(145deg, var(--color-bg-card) 0%, var(--color-bg-subtle) 100%);
  border: 1px solid var(--color-border);
  border-left: 4px solid var(--color-accent-emerald);
  border-radius: var(--radius-md);
  padding: 1.35rem 1.5rem;
  box-shadow: var(--shadow-sm);
}

.takeaways-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--color-accent-emerald);
  margin-bottom: 0.85rem;
}

.takeaways-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.takeaways-item {
  display: flex;
  align-items: flex-start;
  gap: 0.6rem;
  font-size: 0.95rem;
  color: var(--color-text-main);
  line-height: 1.5;
}

.takeaway-bullet {
  color: var(--color-accent-emerald);
  font-size: 1.1rem;
  line-height: 1;
  padding-top: 2px;
}

/* Mark Complete Action Card */
.lesson-action-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.25rem;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  margin-top: 1rem;
}

.mark-complete-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.6rem 1.2rem;
  border-radius: var(--radius-md);
  font-size: 0.9rem;
  font-weight: 600;
  background: var(--color-bg-surface);
  color: var(--color-text-main);
  border: 1px solid var(--color-border);
  transition: all 0.15s ease;
}

.mark-complete-btn:hover {
  background: var(--color-bg-hover);
  border-color: var(--color-border-focus);
}

.mark-complete-btn.is-completed {
  background: var(--color-accent-emerald);
  color: #ffffff;
  border-color: var(--color-accent-emerald);
}

/* Prev / Next Navigation */
.prev-next-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  margin-top: 1.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--color-border);
}

.nav-link-card {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  padding: 1rem 1.25rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  background: var(--color-bg-card);
  color: var(--color-text-main);
  text-decoration: none !important;
  transition: all 0.15s ease;
}

.nav-link-card:hover {
  border-color: var(--color-primary);
  background: var(--color-bg-hover);
  transform: translateY(-2px);
  box-shadow: var(--shadow-sm);
}

.nav-link-card.next {
  text-align: right;
  align-items: flex-end;
}

.nav-direction-label {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  color: var(--color-text-muted);
  display: flex;
  align-items: center;
  gap: 0.35rem;
}

.nav-target-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--color-primary);
  line-height: 1.35;
}

/* Overview / Home Page Screen */
.portal-hero {
  padding: 2.5rem 0 1.5rem;
  text-align: center;
  max-width: 720px;
  margin: 0 auto;
}

.portal-hero-title {
  font-size: 2.5rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.2;
  margin-bottom: 1rem;
  background: linear-gradient(135deg, var(--color-text-main) 30%, var(--color-primary) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.portal-hero-subtitle {
  font-size: 1.1rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
  margin-bottom: 2rem;
}

.cert-overview-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.5rem;
  margin-top: 1rem;
}

.cert-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  transition: all 0.2s ease;
  box-shadow: var(--shadow-sm);
}

.cert-card:hover {
  border-color: var(--color-primary);
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
}

.cert-card-code {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--color-primary);
  text-transform: uppercase;
}

.cert-card-title {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--color-text-main);
}

.cert-card-desc {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  line-height: 1.5;
  flex: 1;
}

/* Cert Card Modules List */
.cert-modules-list {
  margin: 0.5rem 0 0.75rem;
  border-top: 1px solid var(--color-border);
  padding-top: 0.65rem;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.cert-module-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.8rem;
  color: var(--color-text-secondary);
  padding: 0.25rem 0.5rem;
  border-radius: var(--radius-sm);
  background: var(--color-bg-subtle, rgba(255, 255, 255, 0.02));
  border: 1px solid rgba(255, 255, 255, 0.03);
}

.cert-module-name {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  margin-right: 0.5rem;
  font-weight: 500;
}

.cert-module-count {
  font-weight: 600;
  color: var(--color-text-muted);
  flex-shrink: 0;
  font-size: 0.72rem;
}

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

.start-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.45rem 1rem;
  border-radius: var(--radius-md);
  background: var(--color-primary);
  color: #ffffff !important;
  font-weight: 600;
  font-size: 0.85rem;
  transition: opacity 0.15s ease;
}

.start-btn:hover {
  opacity: 0.9;
}

/* --- 8. Search Modal --- */
.search-modal {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 100;
}

.search-modal.active {
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding: 10vh 1rem 2rem;
}

.search-modal-backdrop {
  position: absolute;
  inset: 0;
  background: rgba(0, 0, 0, 0.6);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
}

.search-modal-dialog {
  position: relative;
  width: 100%;
  max-width: 640px;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-modal);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  max-height: 75vh;
  animation: modalSlideDown 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

@keyframes modalSlideDown {
  from {
    opacity: 0;
    transform: translateY(-12px) scale(0.98);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

.search-modal-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 1rem 1.25rem;
  border-bottom: 1px solid var(--color-border);
  color: var(--color-text-muted);
}

.search-input {
  flex: 1;
  background: transparent;
  border: none;
  outline: none;
  font-size: 1.05rem;
  color: var(--color-text-main);
  font-family: inherit;
}

.search-modal-body {
  flex: 1;
  overflow-y: auto;
  max-height: 400px;
}

.search-results {
  display: flex;
  flex-direction: column;
}

.search-hint {
  padding: 2rem 1rem;
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.9rem;
}

.search-result-item {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  padding: 0.85rem 1.25rem;
  border-bottom: 1px solid var(--color-border-subtle);
  color: var(--color-text-main);
  text-decoration: none;
  cursor: pointer;
  transition: background 0.15s ease;
}

.search-result-item:hover, .search-result-item.selected {
  background: var(--color-bg-hover);
  text-decoration: none;
}

.search-result-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
}

.search-result-title {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--color-text-main);
}

.search-result-cert {
  font-size: 0.7rem;
  padding: 0.15rem 0.45rem;
  border-radius: var(--radius-sm);
  background: var(--color-primary-light);
  color: var(--color-primary);
  font-weight: 600;
  text-transform: uppercase;
}

.search-result-snippet {
  font-size: 0.82rem;
  color: var(--color-text-secondary);
  line-height: 1.4;
  overflow: hidden;
  text-overflow: ellipsis;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
}

.search-result-tags {
  display: flex;
  gap: 0.35rem;
  margin-top: 0.2rem;
}

.search-modal-footer {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 1rem;
  padding: 0.65rem 1.25rem;
  border-top: 1px solid var(--color-border);
  background: var(--color-bg-subtle);
  font-size: 0.75rem;
  color: var(--color-text-muted);
}

/* --- 9. Tables, Callouts & Markdown Enhancements --- */
.table-responsive {
  width: 100%;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: 1.5rem 0;
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  background: var(--color-bg-surface);
  box-shadow: var(--shadow-sm);
}

.markdown-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.9rem;
}

.markdown-table th,
.markdown-table td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--color-border);
}

.markdown-table th {
  background: var(--color-bg-subtle);
  font-weight: 600;
  color: var(--color-text-main);
  white-space: nowrap;
}

.markdown-table tr:last-child td {
  border-bottom: none;
}

.markdown-table tr:hover {
  background: rgba(255, 255, 255, 0.02);
}

blockquote,
.callout {
  margin: 1.5rem 0;
  padding: 1rem 1.25rem;
  border-left: 4px solid var(--color-accent-indigo);
  background: var(--color-bg-subtle);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  font-size: 0.95rem;
  line-height: 1.6;
}

.callout-warning {
  border-left-color: #f59e0b;
  background: rgba(245, 158, 11, 0.08);
}

.callout-tip {
  border-left-color: #10b981;
  background: rgba(16, 185, 129, 0.08);
}

.callout-note {
  border-left-color: #3b82f6;
  background: rgba(59, 130, 246, 0.08);
}

/* --- 10. Mobile Bottom Action Bar --- */
.mobile-bottom-bar {
  display: none;
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: 60px;
  background: var(--color-bg-header);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-top: 1px solid var(--color-border);
  box-shadow: 0 -4px 16px rgba(0, 0, 0, 0.18);
  z-index: 45;
  padding: 0 0.75rem;
  padding-bottom: max(0px, env(safe-area-inset-bottom));
  align-items: center;
  justify-content: space-around;
}

.mobile-bar-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 3px;
  background: none;
  border: none;
  color: var(--color-text-secondary);
  font-size: 0.68rem;
  font-weight: 500;
  cursor: pointer;
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  transition: all 0.15s ease;
  min-width: 58px;
  min-height: 48px;
}

.mobile-bar-btn:active {
  transform: scale(0.96);
  background: var(--color-bg-subtle);
}

.mobile-bar-btn svg {
  stroke-width: 2.2;
}

.mobile-bar-btn.complete-btn .custom-checkbox-circle {
  width: 19px;
  height: 19px;
  border-radius: 50%;
  border: 2px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s ease;
}

.mobile-bar-btn.complete-btn.completed {
  color: var(--color-accent-emerald);
}

.mobile-bar-btn.complete-btn.completed .custom-checkbox-circle {
  background: var(--color-accent-emerald);
  border-color: var(--color-accent-emerald);
  color: #ffffff;
}

.mobile-bar-btn.complete-btn:not(.completed) .custom-checkbox-circle svg {
  display: none;
}

.mobile-bar-btn.next-btn {
  color: var(--color-accent-indigo);
  font-weight: 600;
}

/* --- 11. Responsive Breakpoints --- */

/* Desktop Guard: strictly hide mobile bottom bar above 1024px */
@media (min-width: 1025px) {
  .mobile-bottom-bar {
    display: none !important;
  }
}

/* Tablet (iPad portrait / landscape <= 1024px) */
@media (max-width: 1024px) {
  :root {
    --sidebar-width: 280px;
  }

  .mobile-only {
    display: flex;
  }

  /* Header adjustments for tablet: prevent horizontal blowout */
  .top-header {
    padding: 0 0.85rem;
    gap: 0.5rem;
    max-width: 100vw;
  }

  .header-left, .header-right {
    gap: 0.5rem;
  }

  /* Hide cert tabs in header on tablet/mobile (filter available in sidebar) */
  .cert-nav-tabs {
    display: none;
  }

  .brand-badge {
    display: none;
  }

  .brand-title {
    font-size: 0.92rem;
  }

  .search-trigger-btn {
    min-width: unset;
    padding: 0.4rem 0.65rem;
  }

  .search-placeholder {
    display: inline-block;
    max-width: 110px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
  }

  .progress-widget .progress-label,
  .progress-widget .progress-count {
    display: none;
  }

  .progress-bar-container {
    width: 48px;
    height: 5px;
  }

  /* Reading Area on Tablet */
  .reading-area {
    padding: 1.5rem 1.25rem 6.5rem;
    width: 100%;
    max-width: 100%;
    min-width: 0;
    box-sizing: border-box;
  }

  /* Sidebar Drawer on Tablet */
  .sidebar {
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    height: 100vh;
    height: 100dvh;
    width: min(340px, 85vw);
    transform: translateX(-100%);
    transition: transform 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: var(--shadow-modal);
    z-index: 100;
    background: var(--color-bg-surface);
  }

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

  .sidebar-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.6);
    z-index: 99;
    backdrop-filter: blur(4px);
  }

  .sidebar-backdrop.open {
    display: block;
  }

  .sidebar-curriculum {
    padding-bottom: 7rem; /* Never let bottom items be obscured by mobile action bar */
  }

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

  .mobile-bottom-bar {
    display: flex;
  }

  .table-responsive {
    display: block;
    width: 100%;
    max-width: 100%;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }

  .markdown-table {
    min-width: 460px;
    width: 100%;
  }

  .cert-overview-grid {
    grid-template-columns: repeat(auto-fit, minmax(min(100%, 280px), 1fr));
    gap: 1.25rem;
  }
}

/* Mobile Devices (<= 768px) */
@media (max-width: 768px) {
  .top-header {
    padding: 0 0.65rem;
    gap: 0.4rem;
  }

  .header-left {
    gap: 0.4rem;
  }

  .brand-logo {
    gap: 0.5rem;
  }

  .logo-icon {
    width: 32px;
    height: 32px;
  }

  .brand-title {
    font-size: 0.88rem;
    max-width: 140px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
  }

  .search-placeholder,
  .search-kbd {
    display: none;
  }

  .search-trigger-btn {
    min-width: 36px;
    width: 36px;
    height: 36px;
    padding: 0;
    justify-content: center;
  }

  .progress-widget {
    padding: 0.35rem 0.45rem;
  }

  .progress-percent {
    font-size: 0.78rem;
  }

  .progress-bar-container {
    width: 36px;
    height: 4px;
  }

  .reading-area {
    padding: 1rem 0.75rem 6.5rem;
    width: 100%;
    max-width: 100%;
    min-width: 0;
    box-sizing: border-box;
  }

  .lesson-main-title {
    font-size: 1.35rem;
    line-height: 1.3;
  }

  .lesson-lead {
    font-size: 0.92rem;
  }

  .key-concept-card,
  .takeaways-card {
    padding: 1rem 0.85rem;
    margin: 1.25rem 0;
    border-radius: var(--radius-md);
  }

  .lesson-section {
    margin: 1.75rem 0;
  }

  .lesson-section-heading {
    font-size: 1.15rem;
  }

  .code-block-wrapper {
    margin: 1rem 0;
    max-width: 100%;
    min-width: 0;
  }

  .code-pre {
    padding: 0.75rem;
    font-size: 0.8rem;
    max-width: 100%;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }

  .prev-next-nav {
    grid-template-columns: 1fr;
    gap: 0.75rem;
    margin-top: 1.75rem;
  }

  .nav-link-card.next {
    text-align: left;
    align-items: flex-start;
  }

  /* Search Modal Bottom-Sheet on Mobile */
  .search-modal {
    padding: 0;
    align-items: flex-end;
  }

  .search-modal-dialog {
    width: 100%;
    max-height: 85vh;
    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
    margin: 0;
  }

  .search-modal-header {
    padding: 0.85rem 1rem;
  }

  .search-modal-footer {
    display: none;
  }
}

/* Small Mobile (< 420px) */
@media (max-width: 420px) {
  .top-header {
    padding: 0 0.5rem;
  }

  .brand-title {
    display: none; /* Icon only to prevent layout breakage on narrow phones */
  }

  .progress-widget .progress-bar-container {
    display: none;
  }

  .reading-area {
    padding: 0.85rem 0.6rem 6.5rem;
  }

  .lesson-item {
    padding: 0.6rem 0.5rem;
  }
}