/* ===== Course Website Design System ===== */
/* Academic Noir — consistent with Lingma-Intro */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;500&display=swap');

:root {
  --color-bg:           #0a0e1a;
  --color-bg-card:      #111827;
  --color-bg-card-alt:  #151d2e;
  --color-bg-section:   #0d1220;
  --color-primary:      #60a5fa;
  --color-primary-dim:  #3b82f620;
  --color-accent:       #818cf8;
  --color-accent2:      #34d399;
  --color-text:         #e2e8f0;
  --color-text-bright:  #f8fafc;
  --color-text-muted:   #94a3b8;
  --color-border:       #1e293b;
  --color-border-hover: #334155;
  --color-danger:       #f87171;
  --color-warning:      #fbbf24;
  --color-success:      #34d399;
  --radius:             12px;
  --radius-sm:          8px;
  --shadow:             0 4px 24px rgba(0,0,0,0.4);
  --transition:         all 0.3s ease;
}

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

html { scroll-behavior: smooth; scroll-padding-top: 70px; }

body {
  font-family: 'Inter', -apple-system, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--color-primary); text-decoration: none; transition: var(--transition); }
a:hover { color: var(--color-accent); }

code {
  font-family: 'JetBrains Mono', monospace;
  background: #1e293b;
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.85em;
  color: var(--color-accent);
}

kbd {
  display: inline-block;
  padding: 2px 8px;
  font-size: 0.8rem;
  font-family: 'JetBrains Mono', monospace;
  background: #1e293b;
  border: 1px solid #334155;
  border-radius: 4px;
  color: var(--color-text);
}

/* ===== Navbar ===== */
.navbar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  background: rgba(10,14,26,0.85);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid transparent;
  transition: var(--transition);
  padding: 0 2rem;
}
.navbar.scrolled { border-bottom-color: var(--color-border); }
.nav-inner { max-width: 1200px; margin: 0 auto; display: flex; align-items: center; justify-content: space-between; height: 60px; }
.nav-brand { font-weight: 700; font-size: 1.1rem; color: var(--color-text-bright); display: flex; align-items: center; gap: 8px; }
.nav-brand .icon { font-size: 1.4rem; }
.nav-links { display: flex; gap: 0.3rem; flex-wrap: wrap; }
.nav-links a {
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--color-text-muted);
  transition: var(--transition);
  white-space: nowrap;
}
.nav-links a:hover, .nav-links a.active { color: var(--color-text-bright); background: var(--color-primary-dim); }

/* Hamburger */
.hamburger { display: none; background: none; border: none; cursor: pointer; padding: 6px; }
.hamburger span { display: block; width: 22px; height: 2px; background: var(--color-text); margin: 5px 0; transition: var(--transition); border-radius: 2px; }
.hamburger.open span:nth-child(1) { transform: rotate(45deg) translate(5px,5px); }
.hamburger.open span:nth-child(2) { opacity: 0; }
.hamburger.open span:nth-child(3) { transform: rotate(-45deg) translate(5px,-5px); }

/* ===== Hero ===== */
.hero {
  min-height: 50vh;
  display: flex; align-items: center; justify-content: center;
  text-align: center;
  padding: 100px 2rem 60px;
  position: relative;
  overflow: hidden;
  background: linear-gradient(135deg, #0a0e1a 0%, #111827 50%, #0d1a2d 100%);
}
.hero::before {
  content: '';
  position: absolute; inset: 0;
  background: radial-gradient(ellipse at 30% 40%, rgba(96,165,250,0.08) 0%, transparent 60%),
              radial-gradient(ellipse at 70% 60%, rgba(129,140,248,0.06) 0%, transparent 50%);
}
.hero-content { position: relative; z-index: 1; max-width: 800px; }
.hero h1 { font-size: 2.8rem; font-weight: 800; color: var(--color-text-bright); margin-bottom: 0.8rem; line-height: 1.2; }
.hero h1 .accent { background: linear-gradient(135deg, var(--color-primary), var(--color-accent)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
.hero .subtitle { font-size: 1.15rem; color: var(--color-text-muted); margin-bottom: 1.5rem; }
.hero-meta { display: flex; gap: 1.5rem; justify-content: center; flex-wrap: wrap; font-size: 0.9rem; color: var(--color-text-muted); }
.hero-meta span { display: flex; align-items: center; gap: 6px; }

/* ===== Sections ===== */
.section { padding: 4rem 2rem; }
.section-alt { background: var(--color-bg-section); }
.section-inner { max-width: 1100px; margin: 0 auto; }
.section-title {
  font-size: 1.8rem; font-weight: 800; color: var(--color-text-bright);
  margin-bottom: 0.5rem;
}
.section-subtitle {
  font-size: 1rem; color: var(--color-text-muted); margin-bottom: 2.5rem;
  max-width: 700px;
}

/* ===== Week Cards ===== */
.week-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 1rem; }

.week-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: var(--transition);
  cursor: pointer;
}
.week-card:hover { border-color: var(--color-border-hover); transform: translateY(-2px); box-shadow: var(--shadow); }
.week-card.current { border-color: var(--color-primary); box-shadow: 0 0 20px rgba(96,165,250,0.15); }
.week-card.current .week-header { background: linear-gradient(135deg, rgba(96,165,250,0.15), rgba(129,140,248,0.1)); }

.week-header { padding: 1rem 1.2rem; display: flex; align-items: center; gap: 1rem; }
.week-num {
  min-width: 44px; height: 44px;
  border-radius: 10px;
  background: var(--color-bg-card-alt);
  display: flex; align-items: center; justify-content: center;
  font-weight: 700; font-size: 0.95rem; color: var(--color-primary);
  border: 1px solid var(--color-border);
}
.week-card.current .week-num { background: var(--color-primary); color: #fff; border-color: var(--color-primary); }
.week-title { font-weight: 600; font-size: 0.95rem; color: var(--color-text-bright); }
.week-module { font-size: 0.75rem; color: var(--color-text-muted); margin-top: 2px; }

.week-body {
  display: none;
  padding: 0 1.2rem 1.2rem;
  border-top: 1px solid var(--color-border);
  animation: fadeIn 0.3s ease;
}
.week-body.open { display: block; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(-8px); } to { opacity: 1; transform: translateY(0); } }

.week-body h4 { font-size: 0.85rem; font-weight: 600; color: var(--color-primary); margin: 1rem 0 0.4rem; }
.week-body ul { padding-left: 1.2rem; font-size: 0.85rem; color: var(--color-text-muted); }
.week-body ul li { margin-bottom: 0.25rem; }
.week-body .hw-box {
  margin-top: 0.8rem;
  padding: 0.8rem 1rem;
  background: rgba(251,191,36,0.08);
  border-left: 3px solid var(--color-warning);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  font-size: 0.85rem;
  color: var(--color-text-muted);
}
.week-body .hw-box strong { color: var(--color-warning); }

/* ===== Info Cards ===== */
.info-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 1rem; }

.info-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.5rem;
  transition: var(--transition);
}
.info-card:hover { border-color: var(--color-border-hover); }
.info-card .icon { font-size: 1.8rem; margin-bottom: 0.8rem; display: block; }
.info-card h3 { font-size: 1rem; font-weight: 600; color: var(--color-text-bright); margin-bottom: 0.4rem; }
.info-card p { font-size: 0.88rem; color: var(--color-text-muted); }
.info-card a.card-link {
  display: inline-block; margin-top: 0.8rem;
  font-size: 0.85rem; font-weight: 600; color: var(--color-primary);
}

/* ===== Tables ===== */
.table-wrap { overflow-x: auto; -webkit-overflow-scrolling: touch; }
.data-table { width: 100%; border-collapse: collapse; margin: 1rem 0; min-width: 500px; }
.data-table th, .data-table td {
  padding: 0.7rem 1rem;
  text-align: left;
  border-bottom: 1px solid var(--color-border);
  font-size: 0.88rem;
}
.data-table th { color: var(--color-text-muted); font-weight: 600; font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.5px; }
.data-table td { color: var(--color-text); }
.data-table tbody tr:hover { background: var(--color-primary-dim); }

/* ===== Topic Cards (Final Project) ===== */
.topic-category { margin-bottom: 2rem; }
.topic-category h3 { font-size: 1.1rem; font-weight: 700; color: var(--color-text-bright); margin-bottom: 1rem; display: flex; align-items: center; gap: 8px; }
.topic-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 0.8rem; }
.topic-item {
  background: var(--color-bg-card-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: 1rem 1.2rem;
  transition: var(--transition);
}
.topic-item:hover { border-color: var(--color-border-hover); }
.topic-item h4 { font-size: 0.9rem; font-weight: 600; color: var(--color-text-bright); margin-bottom: 0.3rem; }
.topic-item p { font-size: 0.8rem; color: var(--color-text-muted); }
.topic-item .difficulty { font-size: 0.75rem; margin-top: 0.4rem; color: var(--color-warning); }

/* ===== FAQ ===== */
.faq-item { border-bottom: 1px solid var(--color-border); }
.faq-q {
  display: flex; align-items: center; justify-content: space-between;
  padding: 1rem 0;
  cursor: pointer;
  font-weight: 600; font-size: 0.95rem; color: var(--color-text-bright);
  transition: var(--transition);
}
.faq-q:hover { color: var(--color-primary); }
.faq-q .chevron { transition: transform 0.3s; font-size: 0.8rem; color: var(--color-text-muted); }
.faq-item.open .faq-q .chevron { transform: rotate(180deg); }
.faq-a { display: none; padding: 0 0 1rem; font-size: 0.9rem; color: var(--color-text-muted); line-height: 1.8; }
.faq-item.open .faq-a { display: block; }

/* ===== Resource Cards ===== */
.resource-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 1rem; }
.resource-card {
  display: flex; align-items: center; gap: 1rem;
  padding: 1rem 1.2rem;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  transition: var(--transition);
  text-decoration: none;
}
.resource-card:hover { border-color: var(--color-primary); transform: translateY(-2px); box-shadow: var(--shadow); }
.resource-card .res-icon { font-size: 1.6rem; }
.resource-card h4 { font-size: 0.9rem; font-weight: 600; color: var(--color-text-bright); }
.resource-card p { font-size: 0.78rem; color: var(--color-text-muted); }

/* ===== Alert Boxes ===== */
.alert { padding: 1rem 1.2rem; border-radius: var(--radius-sm); margin: 1rem 0; display: flex; gap: 10px; font-size: 0.9rem; }
.alert .alert-icon { font-size: 1.1rem; flex-shrink: 0; }
.alert-info { background: rgba(96,165,250,0.1); border-left: 3px solid var(--color-primary); color: var(--color-text-muted); }
.alert-warning { background: rgba(251,191,36,0.08); border-left: 3px solid var(--color-warning); color: var(--color-text-muted); }
.alert-success { background: rgba(52,211,153,0.08); border-left: 3px solid var(--color-success); color: var(--color-text-muted); }

/* ===== Checklist ===== */
.checklist { list-style: none; padding: 0; }
.checklist li { padding: 0.5rem 0; font-size: 0.9rem; color: var(--color-text-muted); display: flex; align-items: flex-start; gap: 8px; }
.checklist li::before { content: '☐'; color: var(--color-primary); font-size: 1rem; flex-shrink: 0; }

/* ===== Badge ===== */
.badge {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 99px;
  font-size: 0.72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.badge-current { background: var(--color-primary); color: #fff; }
.badge-done { background: var(--color-success); color: #0a0e1a; }
.badge-upcoming { background: var(--color-border); color: var(--color-text-muted); }

/* ===== Feature Highlights ===== */
.feature-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 1rem; margin: 1.5rem 0; }
.feature-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.2rem;
  text-align: center;
  transition: var(--transition);
}
.feature-card:hover { border-color: var(--color-primary); transform: translateY(-2px); }
.feature-card .feat-icon { font-size: 2rem; margin-bottom: 0.6rem; display: block; }
.feature-card h4 { font-size: 0.9rem; font-weight: 600; color: var(--color-text-bright); margin-bottom: 0.3rem; }
.feature-card p { font-size: 0.8rem; color: var(--color-text-muted); }

/* ===== Footer ===== */
.footer {
  text-align: center;
  padding: 2.5rem 2rem;
  border-top: 1px solid var(--color-border);
  font-size: 0.85rem;
  color: var(--color-text-muted);
}
.footer-links { display: flex; justify-content: center; gap: 1.5rem; margin-top: 1rem; flex-wrap: wrap; }
.footer-links a { color: var(--color-text-muted); font-size: 0.82rem; transition: var(--transition); }
.footer-links a:hover { color: var(--color-primary); }

/* ===== Scroll to Top ===== */
.scroll-top {
  position: fixed; bottom: 2rem; right: 2rem; z-index: 99;
  width: 44px; height: 44px;
  border-radius: 50%;
  background: var(--color-primary);
  color: #fff;
  border: none;
  cursor: pointer;
  font-size: 1.2rem;
  display: flex; align-items: center; justify-content: center;
  opacity: 0; transform: translateY(20px);
  transition: var(--transition);
  box-shadow: 0 4px 16px rgba(96,165,250,0.3);
}
.scroll-top.visible { opacity: 1; transform: translateY(0); }
.scroll-top:hover { background: var(--color-accent); }

/* ===== Animations ===== */
.fade-in { opacity: 0; transform: translateY(20px); transition: opacity 0.6s ease, transform 0.6s ease; }
.fade-in.visible { opacity: 1; transform: translateY(0); }

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .hero h1 { font-size: 1.8rem; }
  .hero .subtitle { font-size: 0.95rem; }
  .hero-meta { flex-direction: column; align-items: center; gap: 0.5rem; }
  .hamburger { display: block; }
  .nav-links {
    display: none;
    position: absolute; top: 60px; left: 0; right: 0;
    background: rgba(10,14,26,0.98);
    flex-direction: column;
    padding: 1rem 2rem;
    border-bottom: 1px solid var(--color-border);
  }
  .nav-links.open { display: flex; }
  .nav-links a { padding: 10px 0; font-size: 0.95rem; }
  .section { padding: 2.5rem 1rem; }
  .week-grid { grid-template-columns: 1fr; }
  .info-grid { grid-template-columns: 1fr; }
  .topic-list { grid-template-columns: 1fr; }
  .feature-grid { grid-template-columns: repeat(2, 1fr); }
  .resource-grid { grid-template-columns: 1fr; }
}