/* ==========================================================================
   Academic Archive — Neo S. C. Kao
   ========================================================================== */

/* ---------- Design Tokens ---------- */
:root {
  --color-bg: #f7f9fc;
  --color-surface: #ffffff;
  --color-border: #e4e9f0;
  --color-border-strong: #cfd8e3;

  --color-text: #1e293b;
  --color-text-soft: #475569;
  --color-text-muted: #64748b;

  --color-primary: #1d4ed8;
  --color-primary-dark: #1e3a8a;
  --color-primary-soft: #eff4ff;

  --color-accent: #d97706;
  --color-accent-soft: #fef3c7;

  --color-pdf: #dc2626;
  --color-code: #0ea5e9;

  --shadow-sm: 0 1px 2px rgba(15, 23, 42, 0.04);
  --shadow-md: 0 4px 16px rgba(15, 23, 42, 0.06);
  --shadow-lg: 0 10px 30px rgba(15, 23, 42, 0.08);

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;

  --font-sans: 'Inter', 'Noto Sans TC', system-ui, -apple-system, sans-serif;
  --font-serif: 'Noto Serif TC', 'Georgia', serif;
}

/* ---------- Base ---------- */
* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: 1360px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* ---------- Hero Header ---------- */
.hero-header {
  background: #002855;
  color: #fff;
  padding: 4rem 1.5rem 3rem;
  position: relative;
  overflow: hidden;
}

.hero-header .container {
  position: relative;
  z-index: 1;
}

.hero-header::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    radial-gradient(circle at 20% 20%, rgba(255, 255, 255, 0.12), transparent 40%),
    radial-gradient(circle at 80% 80%, rgba(255, 255, 255, 0.08), transparent 40%);
  pointer-events: none;
}

.hero-content .badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: rgba(255, 255, 255, 0.15);
  border: 1px solid rgba(255, 255, 255, 0.25);
  padding: 0.35rem 0.9rem;
  border-radius: 999px;
  font-size: 0.8rem;
  font-weight: 500;
  letter-spacing: 0.03em;
  backdrop-filter: blur(6px);
}
.hero-content h1 {
  font-family: var(--font-serif);
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 700;
  margin: 1rem 0 0.75rem;
  letter-spacing: -0.02em;
}
.hero-content .subtitle {
  font-size: 1.05rem;
  color: rgba(255, 255, 255, 0.85);
  max-width: 700px;
  margin: 0 0 2rem;
}
.hero-content .subtitle strong { color: #fff; font-weight: 600; }

/* Search box */
.search-box {
  position: relative;
  max-width: 560px;
}
.search-box .search-icon {
  position: absolute;
  left: 1.1rem;
  top: 50%;
  transform: translateY(-50%);
  color: var(--color-text-muted);
  font-size: 0.95rem;
}
.search-box input {
  width: 100%;
  padding: 0.95rem 1.2rem 0.95rem 2.8rem;
  border: none;
  border-radius: var(--radius-md);
  background: #fff;
  font-family: inherit;
  font-size: 0.95rem;
  color: var(--color-text);
  box-shadow: var(--shadow-md);
  transition: box-shadow 0.2s ease, transform 0.2s ease;
}
.search-box input:focus {
  outline: none;
  box-shadow: 0 0 0 4px rgba(255, 255, 255, 0.25), var(--shadow-lg);
}

/* ---------- Page body: main + sidebar side-by-side ---------- */
.page-body {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 240px;
  gap: 2rem;
  padding: 3rem 1.5rem 4rem;
  align-items: start;
}

.main-layout {
  display: flex;
  flex-direction: column;
  gap: 2rem;
  min-width: 0;
}

/* ---------- Category Card ---------- */
.category {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.75rem 1.75rem 1.5rem;
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.25s ease, transform 0.25s ease;
  scroll-margin-top: 1.5rem;
}
.category:hover {
  box-shadow: var(--shadow-md);
}

.category-header {
  display: flex;
  align-items: center;
  gap: 0.9rem;
  padding-bottom: 1rem;
  margin-bottom: 1.25rem;
  border-bottom: 1px solid var(--color-border);
}
.category-icon {
  width: 44px;
  height: 44px;
  border-radius: 10px;
  display: grid;
  place-items: center;
  background: var(--color-primary-soft);
  color: var(--color-primary);
  font-size: 1.1rem;
  flex-shrink: 0;
}
.category-icon.code-icon {
  background: #e0f2fe;
  color: var(--color-code);
}
.category-title {
  font-family: var(--font-serif);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text);
  margin: 0;
  letter-spacing: -0.01em;
}

/* Highlighted category (My Publications) */
.highlighted-category {
  background: linear-gradient(180deg, #fffbeb 0%, #ffffff 60%);
  border-color: #fde68a;
}
.highlighted-category .category-icon {
  background: var(--color-accent-soft);
  color: var(--color-accent);
}
.highlighted-category .category-header {
  border-bottom-color: #fde68a;
}

/* ---------- Subcategories ---------- */
.subcategory { margin-top: 1.25rem; }
.subcategory:first-of-type { margin-top: 0; }

.subcategory-title {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-text-soft);
  margin: 0 0 0.75rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding-left: 0.25rem;
  font-family: var(--font-serif);
}
.subcategory-title i {
  color: var(--color-primary);
  font-size: 0.85rem;
}
.highlighted-category .subcategory-title i { color: var(--color-accent); }

.sub-subcategory {
  margin-top: 1rem;
  padding-left: 0.75rem;
  border-left: 2px solid var(--color-border);
}
.sub-subcategory-title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-text-muted);
  margin: 0 0 0.6rem;
  display: flex;
  align-items: center;
  gap: 0.45rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}
.sub-subcategory-title i { color: var(--color-text-muted); }

/* ---------- Paper List ---------- */
.paper-list {
  display: flex;
  flex-direction: column;
  gap: 0.1rem;
}

.paper {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.4rem 0.9rem;
  border-radius: var(--radius-sm);
  text-decoration: none;
  color: var(--color-text);
  background: #fafbfc;
  border: 1px solid transparent;
  transition: all 0.18s ease;
  font-size: 0.92rem;
  line-height: 1.30;
}
.paper:hover {
  background: var(--color-primary-soft);
  border-color: #dbe6ff;
  transform: translateX(2px);
}
.paper-icon {
  flex-shrink: 0;
  width: 26px;
  height: 26px;
  border-radius: 6px;
  display: grid;
  place-items: center;
  font-size: 0.9rem;  
}
.pdf-icon { background: #fee2e2; color: var(--color-pdf); }
.computer-icon { background: #e0f2fe; color: var(--color-code); }

.paper-text { flex: 1; }
.paper-text em {
  font-style: italic;
  color: var(--color-text-soft);
  font-weight: 500;
}

/* Paper item with tutorial tag */
.paper-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.paper-item .paper { flex: 1; }

.tutorial-tag {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.4rem 0.75rem;
  background: var(--color-primary-soft);
  color: var(--color-primary);
  border: 1px solid #dbe6ff;
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  font-weight: 500;
  text-decoration: none;
  transition: all 0.18s ease;
  white-space: nowrap;
}
.tutorial-tag:hover {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

/* Year badge */
.year-badge {
  display: inline-block;
  padding: 0.1rem 0.55rem;
  margin-left: 0.4rem;
  background: var(--color-primary-soft);
  color: var(--color-primary);
  border-radius: 999px;
  font-size: 0.75rem;
  font-weight: 600;
  font-family: var(--font-sans);
  vertical-align: middle;
}
.highlighted-category .year-badge {
  background: var(--color-accent-soft);
  color: var(--color-accent);
}

/* Author highlight */
.author-highlight {
  color: var(--color-accent);
  font-weight: 700;
  background: linear-gradient(180deg, transparent 65%, var(--color-accent-soft) 65%);
  padding: 0 2px;
}

/* Language tag */
.lang-tag {
  display: inline-block;
  padding: 0.15rem 0.55rem;
  border-radius: 4px;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-left: auto;
  flex-shrink: 0;
  align-self: center;
}
.lang-tag.cpp { background: #dbeafe; color: #1e40af; }
.lang-tag.fortran { background: #f3e8ff; color: #6b21a8; }

.code-paper { align-items: center; }

/* ---------- Sticky Sidebar ---------- */
.floating-sidebar {
  position: sticky;
  top: 2rem;
  align-self: start;
}
.sidebar-card {
  background: var(--color-surface);
  border-radius: var(--radius-md);
  padding: 1.1rem;
  box-shadow: var(--shadow-md);
  border: 1px solid var(--color-border);
  max-height: calc(100vh - 4rem);
  overflow-y: auto;
}
.sidebar-title {
  font-size: 0.95rem;
  font-weight: 700;
  margin: 0 0 0.8rem;
  color: var(--color-text);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding-bottom: 0.6rem;
  border-bottom: 1px solid var(--color-border);
}
.sidebar-title i { color: var(--color-primary); }

.sidebar-nav ul {
  list-style: none;
  padding: 0;
  margin: 0;
}
.sidebar-nav li { margin-bottom: 0.15rem; }
.sidebar-nav a {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  padding: 0.45rem 0.65rem;
  color: var(--color-text-soft);
  text-decoration: none;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  transition: all 0.18s ease;
  position: relative;
}
.sidebar-nav a i {
  width: 16px;
  text-align: center;
  font-size: 0.8rem;
  color: var(--color-text-muted);
}
.sidebar-nav a:hover {
  background: var(--color-primary-soft);
  color: var(--color-primary);
}
.sidebar-nav a:hover i { color: var(--color-primary); }

.sidebar-nav a.highlight-link {
  color: var(--color-accent);
  font-weight: 600;
}
.sidebar-nav a.highlight-link i { color: var(--color-accent); }
.sidebar-nav a.highlight-link:hover {
  background: var(--color-accent-soft);
  color: #b45309;
}

/* Scrollspy active state */
.sidebar-nav a.active {
  background: var(--color-primary-soft);
  color: var(--color-primary);
  font-weight: 600;
}
.sidebar-nav a.active i { color: var(--color-primary); }
.sidebar-nav a.active::before {
  content: "";
  position: absolute;
  left: -0.4rem;
  top: 20%;
  bottom: 20%;
  width: 3px;
  background: var(--color-primary);
  border-radius: 2px;
}
.sidebar-nav a.highlight-link.active {
  background: var(--color-accent-soft);
  color: #b45309;
}
.sidebar-nav a.highlight-link.active::before {
  background: var(--color-accent);
}

/* ---------- Footer ---------- */
.footer {
  text-align: center;
  padding: 2rem 1.5rem;
  color: var(--color-text-muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--color-border);
  background: var(--color-surface);
}
.footer p { margin: 0; }

/* ---------- Responsive ---------- */
@media (max-width: 1100px) {
  .page-body {
    grid-template-columns: 1fr;
  }
  .floating-sidebar { display: none; }
}
@media (max-width: 640px) {
  .hero-header { padding: 3rem 1.25rem 2.5rem; }
  .category { padding: 1.25rem; }
  .category-title { font-size: 1.25rem; }
  .paper { font-size: 0.88rem; }
  .paper-item { flex-direction: column; align-items: stretch; }
  .tutorial-tag { align-self: flex-start; }
}

/* ---------- Search filter helper ---------- */
.paper.hidden,
.paper-item.hidden,
.subcategory.hidden,
.sub-subcategory.hidden,
.category.hidden { display: none; }