/* ==========================================================================
   Leapfrog — Minimal Academic Design System
   ========================================================================== */

/* --- Tokens --- */
:root {
  --color-text: #1a1a1a;
  --color-text-secondary: #555;
  --color-text-muted: #777;
  --color-bg: #fff;
  --color-bg-subtle: #f7f7f7;
  --color-border: #e0e0e0;
  --color-border-light: #eee;
  --color-accent: #2c5282;
  --color-accent-hover: #1a365d;
  --color-active-bg: #f0f4f8;

  --font-body: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, "SFMono-Regular", "SF Mono", Menlo, Consolas, monospace;

  --measure: 42rem;
  --measure-wide: 56rem;
  --sidebar-width: 15rem;

  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
}

/* --- Reset --- */
*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.7;
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

/* --- Site Shell --- */
.site-shell {
  flex: 1;
  width: 100%;
  max-width: var(--measure-wide);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

/* --- Skip Link --- */
.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-md);
  padding: var(--space-xs) var(--space-sm);
  background: var(--color-text);
  color: var(--color-bg);
  font-size: 0.875rem;
  text-decoration: none;
  z-index: 100;
  border-radius: 0 0 4px 4px;
}

.skip-link:focus {
  top: 0;
}

/* ==========================================================================
   Header & Navigation
   ========================================================================== */

.site-header {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  padding: var(--space-lg) 0;
  border-bottom: 1px solid var(--color-border);
}

@media (min-width: 1024px) {
  .site-header {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
  }
}

.brand-wrapper {
  flex-shrink: 0;
}

.brand {
  color: var(--color-text);
  text-decoration: none;
  font-size: 1.125rem;
  font-weight: 600;
  letter-spacing: -0.01em;
}

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

.site-nav {
  flex: 1;
}

.nav-list {
  margin: 0;
  padding: 0;
  list-style: none !important;
  display: flex !important;
  flex-wrap: wrap;
  gap: var(--space-sm) var(--space-md);
}

@media (min-width: 1024px) {
  .nav-list {
    justify-content: flex-end;
    gap: var(--space-md) var(--space-lg);
  }
}

.nav-list li {
  list-style: none !important;
  margin: 0;
  padding: 0;
}

.nav-list a {
  color: var(--color-text-secondary);
  text-decoration: none;
  font-size: 0.8125rem;
  font-weight: 500;
  padding: var(--space-xs) 0;
  border-bottom: 2px solid transparent;
  transition: color 0.15s ease, border-color 0.15s ease;
  white-space: nowrap;
}

@media (min-width: 768px) {
  .nav-list a {
    font-size: 0.9375rem;
  }
}

.nav-list a:hover {
  color: var(--color-text);
}

.nav-list a.is-active {
  color: var(--color-text);
  border-bottom-color: var(--color-accent);
}

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

.search-toggle {
  background: none;
  border: none;
  padding: var(--space-xs);
  cursor: pointer;
  color: var(--color-text-secondary);
}

.search-toggle:hover {
  color: var(--color-text);
}

.search-toggle svg {
  width: 1.25rem;
  height: 1.25rem;
  display: block;
}

/* Mobile toggle removed */

/* ==========================================================================
   Main
   ========================================================================== */

.site-main {
  padding: var(--space-2xl) 0 var(--space-3xl);
}

/* ==========================================================================
   Footer
   ========================================================================== */

.site-footer {
  border-top: 1px solid var(--color-border);
  padding: var(--space-lg) var(--space-lg);
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.875rem;
}

.site-footer p {
  margin: 0;
}

/* ==========================================================================
   Typography
   ========================================================================== */

a {
  color: var(--color-accent);
  text-decoration-color: var(--color-border);
  text-underline-offset: 0.2em;
  transition: color 0.15s ease;
}

a:hover {
  color: var(--color-accent-hover);
  text-decoration-color: var(--color-accent-hover);
}

h1, h2, h3, h4 {
  margin: 0;
  line-height: 1.3;
  font-weight: 600;
  letter-spacing: -0.01em;
}

h1 {
  font-size: 2rem;
}

h2 {
  font-size: 1.5rem;
}

h3 {
  font-size: 1.1875rem;
}

h4 {
  font-size: 1rem;
}

/* ==========================================================================
   Homepage
   ========================================================================== */

.page-intro {
  max-width: var(--measure);
  margin-bottom: var(--space-3xl);
}

.page-intro h1 {
  margin-bottom: var(--space-sm);
}

.page-intro p {
  margin: 0;
  color: var(--color-text-secondary);
  font-size: 1.0625rem;
  line-height: 1.7;
}

.section-heading {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
}

.section-heading h2 {
  font-size: 1.25rem;
}

.section-heading a {
  font-size: 0.875rem;
  white-space: nowrap;
}

/* Post list (homepage + list page) */
.post-list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.post-list li {
  padding: var(--space-md) 0;
  border-bottom: 1px solid var(--color-border-light);
}

.post-list li:first-child {
  padding-top: 0;
}

.post-list li:last-child {
  border-bottom: none;
}

.post-list h3 {
  margin-bottom: var(--space-xs);
}

.post-list h3 a {
  color: var(--color-text);
  text-decoration: none;
}

.post-list h3 a:hover {
  color: var(--color-accent);
}

.post-list .meta {
  margin: 0 0 var(--space-xs);
  color: var(--color-text-muted);
  font-size: 0.875rem;
}

.post-list .summary {
  margin: 0;
  color: var(--color-text-secondary);
  font-size: 0.9375rem;
}

/* Tag list */
.tag-list {
  list-style: none;
  margin: var(--space-lg) 0 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.tag-list a {
  display: inline-block;
  padding: var(--space-xs) var(--space-sm);
  border: 1px solid var(--color-border);
  border-radius: 3px;
  color: var(--color-text-secondary);
  font-size: 0.8125rem;
  text-decoration: none;
  transition: background-color 0.15s ease, border-color 0.15s ease;
}

.tag-list a:hover {
  background: var(--color-bg-subtle);
  border-color: var(--color-border);
  color: var(--color-text);
}

/* ==========================================================================
   Article (Single Page)
   ========================================================================== */

.article {
  max-width: var(--measure);
  margin: 0 auto;
}

.article-header {
  margin-bottom: var(--space-xl);
}

.article-header h1 {
  margin-bottom: var(--space-sm);
}

.article-header .meta {
  margin: 0;
  color: var(--color-text-muted);
  font-size: 0.875rem;
}

.back-link {
  display: inline-block;
  margin-bottom: var(--space-lg);
  color: var(--color-text-secondary);
  font-size: 0.875rem;
  text-decoration: none;
}

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

/* ==========================================================================
   Prose (Article Content)
   ========================================================================== */

.prose {
  color: var(--color-text);
  font-size: 1.0625rem;
  line-height: 1.8;
}

.prose > :first-child {
  margin-top: 0;
}

.prose > :last-child {
  margin-bottom: 0;
}

.prose p,
.prose ul,
.prose ol,
.prose blockquote,
.prose pre {
  margin: var(--space-md) 0;
}

.prose ul,
.prose ol {
  padding-left: 1.5rem;
}

.prose li {
  margin-bottom: var(--space-xs);
}

.prose h2 {
  margin-top: var(--space-2xl);
  margin-bottom: var(--space-sm);
  padding-bottom: var(--space-xs);
  border-bottom: 1px solid var(--color-border-light);
}

.prose h3 {
  margin-top: var(--space-xl);
  margin-bottom: var(--space-sm);
}

.prose h4 {
  margin-top: var(--space-lg);
  margin-bottom: var(--space-xs);
}

.prose blockquote {
  border-left: 3px solid var(--color-border);
  margin-left: 0;
  padding: var(--space-sm) var(--space-lg);
  color: var(--color-text-secondary);
  background: var(--color-bg-subtle);
}

.prose blockquote p {
  margin: var(--space-sm) 0;
}

.prose blockquote p:first-child {
  margin-top: 0;
}

.prose blockquote p:last-child {
  margin-bottom: 0;
}

.prose strong {
  font-weight: 600;
}

/* Code */
pre {
  margin: 0;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  background: var(--color-bg-subtle);
  color: var(--color-text);
  padding: var(--space-md);
  overflow-x: auto;
  font-size: 0.875rem;
  line-height: 1.6;
}

code {
  font-family: var(--font-mono);
  font-size: 0.875em;
}

pre code {
  color: inherit;
}

:not(pre) > code {
  border: 1px solid var(--color-border);
  border-radius: 3px;
  background: var(--color-bg-subtle);
  padding: 0.1em 0.3em;
}

/* ==========================================================================
   List Page
   ========================================================================== */

.list-header {
  max-width: var(--measure);
  margin-bottom: var(--space-xl);
}

.list-header h1 {
  margin-bottom: var(--space-sm);
}

.list-header p {
  margin: 0;
  color: var(--color-text-secondary);
}

/* ==========================================================================
   Course Layout (Wider & Glued)
   ========================================================================== */

/* Remove constraints for course pages */
body:has(.course-layout) .site-shell {
  max-width: none;
  margin: 0;
  padding: 0;
}

body:has(.course-layout) .site-header,
body:has(.course-layout) .site-footer {
  max-width: var(--measure-wide);
  margin: 0 auto;
}

.course-layout {
  display: grid;
  grid-template-columns: var(--sidebar-width) 1fr;
  gap: 0;
  align-items: start;
  min-height: calc(100vh - 100px);
}

/* Sidebar glued to the left */
.course-sidebar {
  position: sticky;
  top: 0;
  height: 100vh;
  padding: var(--space-xl) 0;
  background: var(--color-bg-subtle);
  border-right: 1px solid var(--color-border-light);
  overflow-y: auto;
}

.course-sidebar-header {
  padding: 0 var(--space-lg) var(--space-md);
  border-bottom: 1px solid var(--color-border-light);
  margin-bottom: var(--space-md);
}

.course-sidebar-title {
  font-size: 0.8125rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text);
  text-decoration: none;
  display: block;
}

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

.course-nav-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.course-nav-item {
  margin-bottom: 2px;
}

.course-nav-link {
  display: block;
  padding: var(--space-sm) var(--space-lg);
  color: var(--color-text-secondary);
  text-decoration: none;
  font-size: 0.9375rem;
  transition: all 0.15s ease;
}

.course-nav-link:hover {
  background: rgba(0, 0, 0, 0.03);
  color: var(--color-text);
}

.course-nav-link.is-active {
  color: var(--color-accent);
  background: var(--color-active-bg);
  font-weight: 500;
}

/* Sub-level navigation (nested modules) */
.course-nav-sublist {
  list-style: none;
  margin: 0;
  padding: 0;
  display: none; /* Hidden by default */
  background: rgba(0, 0, 0, 0.015);
}

.course-nav-sublist.is-expanded {
  display: block;
}

.course-nav-subitem a {
  padding-left: var(--space-2xl);
  font-size: 0.875rem;
}

/* Course content area (Wide) */
.course-content {
  padding: var(--space-2xl) var(--space-3xl);
  max-width: 64rem;
  margin: 0 auto;
}

.course-content .article-header {
  margin-bottom: var(--space-2xl);
}

.breadcrumb {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  margin-bottom: var(--space-sm);
}

.breadcrumb a {
  color: inherit;
  text-decoration: none;
}

.breadcrumb a:hover {
  text-decoration: underline;
}

/* CATALOG VIEW */
.course-catalog {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-xl);
  margin-top: var(--space-2xl);
}

.course-card {
  border: 1px solid var(--color-border);
  border-radius: 8px;
  padding: var(--space-lg);
  display: flex;
  flex-direction: column;
}

.course-card-header h2 {
  margin-top: 0;
  font-size: 1.25rem;
}

.course-card-header h2 a {
  color: var(--color-text);
  text-decoration: none;
}

.course-card-header p {
  color: var(--color-text-secondary);
  font-size: 0.9375rem;
  margin-bottom: var(--space-lg);
}

.course-modules-dropdown {
  margin-top: auto;
  border-top: 1px solid var(--color-border-light);
  padding-top: var(--space-md);
}

.course-modules-dropdown summary {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-accent);
  cursor: pointer;
  outline: none;
}

.course-modules-dropdown summary:hover {
  text-decoration: underline;
}

.course-modules-dropdown .module-list {
  list-style: none;
  margin: var(--space-sm) 0 0;
  padding: 0;
}

.course-modules-dropdown .module-list li {
  padding: var(--space-xs) 0;
  font-size: 0.875rem;
  display: flex;
  justify-content: space-between;
  border-bottom: 1px solid var(--color-border-light);
}

.course-modules-dropdown .module-list li:last-child {
  border-bottom: none;
}

.course-modules-dropdown .module-list a {
  color: var(--color-text);
  text-decoration: none;
}

.course-modules-dropdown .module-list a:hover {
  color: var(--color-accent);
}

.course-modules-dropdown .meta {
  color: var(--color-text-muted);
  font-style: italic;
}

/* Course overview page */
.course-overview {
  max-width: var(--measure);
}

.course-overview h1 {
  margin-bottom: var(--space-sm);
}

.course-overview > .summary {
  color: var(--color-text-secondary);
  font-size: 1.0625rem;
  margin: 0 0 var(--space-xl);
}

.module-list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.module-list li {
  padding: var(--space-md) 0;
  border-bottom: 1px solid var(--color-border-light);
}

.module-list li:last-child {
  border-bottom: none;
}

.module-list h3 {
  margin-bottom: var(--space-xs);
}

.module-list h3 a {
  color: var(--color-text);
  text-decoration: none;
}

.module-list h3 a:hover {
  color: var(--color-accent);
}

.module-list .meta {
  margin: 0;
  color: var(--color-text-muted);
  font-size: 0.875rem;
}

/* Prev/Next navigation */
.course-nav {
  display: flex;
  justify-content: space-between;
  gap: var(--space-md);
  margin-top: var(--space-2xl);
  padding-top: var(--space-lg);
  border-top: 1px solid var(--color-border-light);
}

.course-nav a {
  display: block;
  color: var(--color-text-secondary);
  text-decoration: none;
  font-size: 0.9375rem;
  max-width: 50%;
}

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

.course-nav .label {
  display: block;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-xs);
}

.course-nav .next {
  text-align: right;
  margin-left: auto;
}

/* ==========================================================================
   Empty state
   ========================================================================== */

.empty-state {
  padding: var(--space-xl);
  border: 1px dashed var(--color-border);
  color: var(--color-text-muted);
  text-align: center;
}

.empty-state p {
  margin: 0;
}

/* ==========================================================================
   Responsive
   ========================================================================== */

@media (max-width: 768px) {
  .site-shell {
    padding: 0 var(--space-md);
  }

  .site-main {
    padding: var(--space-xl) 0 var(--space-2xl);
  }

  h1 {
    font-size: 1.625rem;
  }

  h2 {
    font-size: 1.3125rem;
  }

  /* Mobile nav always visible */
  .site-header nav {
    order: 2;
  }

  .site-header {
    flex-wrap: wrap;
    gap: var(--space-md);
  }

  /* Course: collapse sidebar */
  .course-layout {
    grid-template-columns: 1fr;
    gap: 0;
  }

  .course-sidebar {
    position: static;
    margin-bottom: var(--space-xl);
    border-bottom: 1px solid var(--color-border-light);
    padding-bottom: var(--space-md);
  }

  .course-sidebar-label {
    display: flex;
    align-items: center;
    justify-content: space-between;
    cursor: pointer;
    padding: var(--space-sm) 0;
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--color-text);
  }

  .course-sidebar-label::after {
    content: "▾";
    font-size: 0.75rem;
    color: var(--color-text-muted);
  }

  .course-sidebar nav {
    display: none;
    padding-top: var(--space-sm);
  }

  .course-sidebar-toggle:checked ~ nav {
    display: block;
  }

  .course-sidebar-toggle:checked ~ .course-sidebar-label::after {
    content: "▴";
  }

  /* Course nav stacks on mobile */
  .course-nav {
    flex-direction: column;
  }

  .course-nav a {
    max-width: 100%;
  }

  .course-nav .next {
    text-align: left;
    margin-left: 0;
  }

  .section-heading {
    flex-direction: column;
    align-items: flex-start;
  }
}

@media (max-width: 480px) {
  h1 {
    font-size: 1.375rem;
  }
}

/* ==========================================================================
   Search Overlay
   ========================================================================== */

.search-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.5);
  display: none;
  align-items: flex-start;
  justify-content: center;
  padding: 10vh var(--space-md);
  z-index: 1000;
  backdrop-filter: blur(4px);
}

.search-overlay.is-visible {
  display: flex;
}

.search-modal {
  background: var(--color-bg);
  width: 100%;
  max-width: 600px;
  border-radius: 8px;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
  overflow: hidden;
  border: 1px solid var(--color-border);
}

#search-input {
  width: 100%;
  padding: var(--space-md) var(--space-lg);
  border: none;
  border-bottom: 1px solid var(--color-border-light);
  font-size: 1.125rem;
  font-family: var(--font-body);
  outline: none;
}

.search-results {
  list-style: none;
  margin: 0;
  padding: 0;
  max-height: 60vh;
  overflow-y: auto;
}

.search-results li a {
  display: block;
  padding: var(--space-md) var(--space-lg);
  text-decoration: none;
  color: var(--color-text);
  border-bottom: 1px solid var(--color-border-light);
  transition: background 0.15s ease;
}

.search-results li:last-child a {
  border-bottom: none;
}

.search-results li a:hover {
  background: var(--color-bg-subtle);
}

.search-result-title {
  display: block;
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.search-result-section {
  font-size: 0.75rem;
  text-transform: uppercase;
  color: var(--color-text-muted);
  letter-spacing: 0.05em;
  margin-bottom: 0.25rem;
  display: block;
}

.search-result-snippet {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  line-height: 1.4;
}

.search-no-results {
  padding: var(--space-lg);
  text-align: center;
  color: var(--color-text-muted);
}

/* ==========================================================================
   Accessibility
   ========================================================================== */

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
  }
}

/* ==========================================================================
   Personal & Library Styles
   ========================================================================== */

.travel-map {
  height: 400px;
  width: 100%;
  margin: var(--space-lg) 0;
  border-radius: 8px;
  border: 1px solid var(--color-border);
  z-index: 1;
}

.city-readout {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  margin-top: var(--space-sm);
}

.library-search {
  width: 100%;
  padding: var(--space-sm) var(--space-md);
  margin-bottom: var(--space-md);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  font-family: var(--font-body);
}

.library-status {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  margin-bottom: var(--space-sm);
}

.library-table-wrapper {
  overflow-x: auto;
  border: 1px solid var(--color-border-light);
  border-radius: 4px;
}

.library-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9375rem;
}

.library-table th {
  text-align: left;
  background: var(--color-bg-subtle);
  padding: var(--space-sm) var(--space-md);
  border-bottom: 2px solid var(--color-border);
}

.library-table td {
  padding: var(--space-sm) var(--space-md);
  border-bottom: 1px solid var(--color-border-light);
}

.library-table tr:hover {
  background: var(--color-bg-subtle);
}

.message {
  padding: var(--space-md);
  background: var(--color-bg-subtle);
  border-left: 4px solid var(--color-accent);
  margin-bottom: var(--space-lg);
  border-radius: 0 4px 4px 0;
}

.personal-section {
  margin-bottom: var(--space-2xl);
}

/* Fix for search toggle svg size */
.search-toggle svg {
  max-width: 100%;
  max-height: 100%;
}