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

:root {
  --bg: #0a0c10;
  --bg-2: #111318;
  --bg-card: #141720;
  --bg-card-hover: #1a1f2e;
  --border: rgba(255,255,255,0.07);
  --border-hover: rgba(255,255,255,0.15);
  --white: #f0f2f5;
  --gray: #8892a4;
  --gray-light: #b0bac8;

  /* Category colors */
  --basics: #4f8ef7;
  --ml: #22c55e;
  --dl: #a855f7;
  --genai: #f59e0b;
  --nlp: #06b6d4;
  --tools: #f43f5e;

  --font-main: 'Noto Sans TC', sans-serif;
  --font-mono: 'Space Grotesk', sans-serif;
  --radius: 12px;
  --radius-sm: 8px;
  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--white);
  font-family: var(--font-main);
  font-size: 15px;
  line-height: 1.7;
  min-height: 100vh;
}

.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 32px;
}

/* ─── Header ────────────────────────────────────── */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(10, 12, 16, 0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 32px;
  height: 64px;
  display: flex;
  align-items: center;
  gap: 40px;
}

.header-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-weight: 600;
  font-size: 16px;
  white-space: nowrap;
}

.logo-icon {
  color: var(--genai);
  font-size: 18px;
}

.header-nav {
  display: flex;
  gap: 4px;
  flex: 1;
}

.header-nav a {
  color: var(--gray);
  text-decoration: none;
  font-size: 14px;
  padding: 6px 14px;
  border-radius: 6px;
  transition: color var(--transition), background var(--transition);
}

.header-nav a:hover,
.header-nav a.active {
  color: var(--white);
  background: rgba(255,255,255,0.06);
}

.header-search {
  display: flex;
  align-items: center;
  gap: 10px;
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 8px 14px;
  min-width: 240px;
}

.header-search input {
  background: none;
  border: none;
  outline: none;
  color: var(--white);
  font-size: 14px;
  font-family: var(--font-main);
  width: 100%;
}

.header-search input::placeholder { color: var(--gray); }

/* ─── Hero Banner ───────────────────────────────── */
.hero-banner {
  position: relative;
  overflow: hidden;
  background: linear-gradient(135deg, #0d1117 0%, #111827 50%, #0d0f1a 100%);
  border-bottom: 1px solid var(--border);
  padding: 80px 32px;
}

.hero-inner {
  position: relative;
  z-index: 2;
  max-width: 1280px;
  margin: 0 auto;
}

.hero-tag {
  display: inline-block;
  background: rgba(245, 158, 11, 0.12);
  border: 1px solid rgba(245, 158, 11, 0.3);
  color: var(--genai);
  font-size: 12px;
  font-weight: 500;
  letter-spacing: 0.08em;
  padding: 5px 14px;
  border-radius: 100px;
  margin-bottom: 24px;
  font-family: var(--font-mono);
}

.hero-banner h1 {
  font-family: var(--font-mono);
  font-size: clamp(36px, 5vw, 64px);
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin-bottom: 20px;
  background: linear-gradient(135deg, #f0f2f5 0%, #8892a4 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-banner p {
  color: var(--gray);
  font-size: 16px;
  line-height: 1.8;
  margin-bottom: 40px;
  max-width: 560px;
}

.hero-stats {
  display: flex;
  gap: 40px;
}

.hero-stat {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.hero-stat strong {
  font-family: var(--font-mono);
  font-size: 32px;
  font-weight: 700;
  color: var(--white);
  line-height: 1;
}

.hero-stat span {
  font-size: 13px;
  color: var(--gray);
}

/* Floating orbs */
.hero-visual {
  position: absolute;
  inset: 0;
  overflow: hidden;
  pointer-events: none;
}

.hero-orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.15;
}

.hero-orb-1 {
  width: 500px; height: 500px;
  background: var(--basics);
  right: -100px; top: -100px;
}

.hero-orb-2 {
  width: 300px; height: 300px;
  background: var(--genai);
  right: 300px; bottom: -50px;
}

.hero-orb-3 {
  width: 200px; height: 200px;
  background: var(--dl);
  right: 100px; top: 50%;
}

/* ─── Filter Tabs ───────────────────────────────── */
.filter-section {
  background: var(--bg-2);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 64px;
  z-index: 90;
}

.filter-tabs {
  display: flex;
  gap: 4px;
  padding: 12px 0;
  overflow-x: auto;
  scrollbar-width: none;
}

.filter-tabs::-webkit-scrollbar { display: none; }

.tab {
  display: flex;
  align-items: center;
  gap: 8px;
  background: none;
  border: 1px solid transparent;
  color: var(--gray);
  font-size: 13px;
  font-family: var(--font-main);
  font-weight: 500;
  padding: 7px 16px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  white-space: nowrap;
  transition: all var(--transition);
}

.tab:hover {
  color: var(--white);
  background: rgba(255,255,255,0.05);
}

.tab.active {
  color: var(--white);
  background: rgba(255,255,255,0.09);
  border-color: var(--border-hover);
}

.tab-count {
  background: rgba(255,255,255,0.1);
  color: var(--gray-light);
  font-size: 11px;
  padding: 1px 7px;
  border-radius: 100px;
}

.tab.active .tab-count {
  background: rgba(255,255,255,0.15);
  color: var(--white);
}

/* ─── Main Content ──────────────────────────────── */
.main-content {
  padding: 60px 0 80px;
}

/* ─── Section Group ─────────────────────────────── */
.section-group {
  margin-bottom: 72px;
  transition: opacity 0.3s, transform 0.3s;
}

.section-group.hidden {
  display: none;
}

.section-header {
  display: flex;
  align-items: center;
  gap: 18px;
  margin-bottom: 32px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--border);
}

.section-icon {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  flex-shrink: 0;
}

.section-icon.basics { background: rgba(79, 142, 247, 0.12); color: var(--basics); }
.section-icon.ml     { background: rgba(34, 197, 94, 0.12);  color: var(--ml); }
.section-icon.dl     { background: rgba(168, 85, 247, 0.12); color: var(--dl); }
.section-icon.genai  { background: rgba(245, 158, 11, 0.12); color: var(--genai); }
.section-icon.nlp    { background: rgba(6, 182, 212, 0.12);  color: var(--nlp); }
.section-icon.tools  { background: rgba(244, 63, 94, 0.12);  color: var(--tools); }

.section-header h2 {
  font-family: var(--font-mono);
  font-size: 22px;
  font-weight: 600;
  margin-bottom: 4px;
}

.section-header p {
  font-size: 13px;
  color: var(--gray);
}

/* ─── Cards Grid ────────────────────────────────── */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 20px;
}

/* ─── Card ──────────────────────────────────────── */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  transition: background var(--transition), border-color var(--transition), transform var(--transition);
  cursor: pointer;
}

.card:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-hover);
  transform: translateY(-2px);
}

.card.hidden {
  display: none;
}

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

.card-num {
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 600;
  color: var(--gray);
  letter-spacing: 0.05em;
}

.card-tag {
  font-size: 11px;
  font-weight: 500;
  padding: 3px 10px;
  border-radius: 100px;
}

/* Card header accent colors */
.card-header.basics .card-tag { background: rgba(79,142,247,0.12); color: var(--basics); }
.card-header.ml .card-tag     { background: rgba(34,197,94,0.12);  color: var(--ml); }
.card-header.dl .card-tag     { background: rgba(168,85,247,0.12); color: var(--dl); }
.card-header.genai .card-tag  { background: rgba(245,158,11,0.12); color: var(--genai); }
.card-header.nlp .card-tag    { background: rgba(6,182,212,0.12);  color: var(--nlp); }
.card-header.tools .card-tag  { background: rgba(244,63,94,0.12);  color: var(--tools); }

.card-title {
  font-family: var(--font-mono);
  font-size: 16px;
  font-weight: 600;
  color: var(--white);
  line-height: 1.4;
}

.card-summary {
  font-size: 13px;
  color: var(--gray-light);
  line-height: 1.7;
}

.card-points {
  display: flex;
  flex-direction: column;
  gap: 6px;
  background: rgba(255,255,255,0.03);
  border-radius: var(--radius-sm);
  padding: 14px;
  border-left: 2px solid rgba(255,255,255,0.08);
}

.point {
  font-size: 12.5px;
  color: var(--gray-light);
  line-height: 1.6;
  font-family: var(--font-mono);
}

.card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: auto;
  padding-top: 14px;
  border-top: 1px solid var(--border);
}

.card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.card-tags span {
  font-size: 11px;
  color: var(--gray);
  background: rgba(255,255,255,0.05);
  padding: 2px 8px;
  border-radius: 4px;
}

.card-meta {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

.meta-time {
  font-size: 11px;
  color: var(--gray);
}

.meta-diff {
  font-size: 11px;
  font-weight: 500;
  padding: 2px 8px;
  border-radius: 4px;
}

.meta-diff.basics { background: rgba(79,142,247,0.12); color: var(--basics); }
.meta-diff.advanced { background: rgba(168,85,247,0.12); color: var(--dl); }

/* ─── No Results ────────────────────────────────── */
.no-results {
  text-align: center;
  padding: 80px 32px;
  color: var(--gray);
}

.no-results-icon { font-size: 48px; margin-bottom: 16px; }
.no-results p { font-size: 16px; }

/* ─── Footer ────────────────────────────────────── */
.site-footer {
  background: var(--bg-2);
  border-top: 1px solid var(--border);
  padding: 32px;
}

.footer-inner {
  max-width: 1280px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 14px;
  font-weight: 500;
}

.footer-note {
  font-size: 13px;
  color: var(--gray);
}

/* ─── Search Highlight ──────────────────────────── */
.highlight {
  background: rgba(245, 158, 11, 0.25);
  color: var(--genai);
  border-radius: 2px;
  padding: 0 2px;
}

/* ─── Responsive ────────────────────────────────── */
@media (max-width: 1024px) {
  .cards-grid {
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  }
}

@media (max-width: 768px) {
  .container { padding: 0 20px; }
  .header-inner { padding: 0 20px; gap: 16px; }
  .header-nav { display: none; }
  .header-search { min-width: 160px; }

  .hero-banner { padding: 60px 20px; }
  .hero-banner h1 { font-size: 36px; }
  .hero-banner p { font-size: 14px; }
  .hero-stats { gap: 24px; }
  .hero-stat strong { font-size: 24px; }

  .filter-tabs { padding: 10px 20px; }
  .main-content { padding: 40px 0 60px; }
  .cards-grid { grid-template-columns: 1fr; }
  .section-group { margin-bottom: 48px; }

  .footer-inner { flex-direction: column; gap: 8px; text-align: center; }
}