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

:root {
  --bg: #070a12;
  --bg-alt: #0d1122;
  --bg-dark: #05070d;
  --surface: #101529;
  --surface-hover: #1e2746;
  --border: rgba(103, 114, 148, 0.35);
  --border-light: rgba(132, 143, 185, 0.45);
  --text: #f2f5ff;
  --text-dim: #b4bdd5;
  --text-muted: #8f98b3;
  --accent: #7aa8ff;
  --accent-dim: #5ea1ff;
  --accent-glow: rgba(122, 168, 255, 0.22);
  --green: #4ade80;
  --amber: #fbbf24;
  --orange: #f59e0b;
  --pink: #f472b6;
  --cyan: #22d3ee;
  --radius: 14px;
  --radius-sm: 10px;
}

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  font-size: 16px;
}

a { color: var(--accent); text-decoration: none; transition: color 0.2s; }
a:hover { color: #93b0ff; }

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ===== Hero ===== */
.hero {
  position: relative;
  padding: 120px 0 80px;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 50% 0%, rgba(108, 140, 255, 0.08) 0%, transparent 70%),
    radial-gradient(ellipse 50% 40% at 80% 20%, rgba(244, 114, 182, 0.05) 0%, transparent 60%);
  pointer-events: none;
}

#hero-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 0;
}

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

.hero h1 {
  font-size: clamp(2.8rem, 6vw, 4.5rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.1;
  margin-bottom: 20px;
}

.hero .accent { color: var(--accent); }

.hero .subtitle {
  font-size: 1.15rem;
  color: var(--text-dim);
  max-width: 600px;
  margin-bottom: 0;
  line-height: 1.6;
}

/* ===== Sticky Bar ===== */
.sticky-bar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(7, 10, 18, 0.88);
  backdrop-filter: blur(9px);
  border-bottom: 1px solid rgba(255,255,255,0.08);
  padding: 18px 0 14px;
  transition: border-color 0.3s, box-shadow 0.3s;
}

.sticky-bar.stuck {
  border-bottom-color: rgba(106, 129, 255, 0.35);
  box-shadow: 0 6px 20px rgba(8, 12, 20, 0.5);
}

.sticky-bar-inner {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.search-input {
  width: 100%;
  max-width: 500px;
  padding: 10px 20px;
  border-radius: 100px;
  border: 1px solid var(--border-light);
  background: var(--surface);
  color: var(--text);
  font-size: 0.9rem;
  font-family: inherit;
  outline: none;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.search-input::placeholder {
  color: var(--text-muted);
}

.search-input:focus {
  border-color: var(--accent-dim);
  box-shadow: 0 0 0 3px var(--accent-glow);
}

.search-meta {
  font-size: 0.75rem;
  color: var(--text-muted);
  padding-left: 20px;
  min-height: 1em;
}

.search-meta:empty {
  display: none;
}

.sticky-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.sticky-nav a {
  display: inline-block;
  padding: 6px 14px;
  border: 1px solid var(--border-light);
  border-radius: 100px;
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--text-dim);
  transition: all 0.2s;
  white-space: nowrap;
}

.sticky-nav a:hover,
.sticky-nav a.active {
  color: var(--text);
  border-color: var(--accent-dim);
  background: var(--accent-glow);
}

/* ===== Sections ===== */
.section {
  padding: 100px 0;
}

.section--alt { background: var(--bg-alt); }
.section--dark { background: var(--bg-dark); }

.section-title {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 14px;
}

.section-desc {
  color: var(--text-dim);
  font-size: 1.05rem;
  margin-bottom: 48px;
  max-width: 640px;
  line-height: 1.6;
}

/* ===== Cards ===== */
.card {
  background: linear-gradient(180deg, rgba(16,22,41,0.95), rgba(17,24,45,0.95));
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.24);
  transition: border-color 0.25s, box-shadow 0.25s, transform 0.25s;
}

.card:hover {
  border-color: var(--accent);
  box-shadow: 0 14px 28px rgba(25, 35, 70, 0.4);
  transform: translateY(-3px);
}

.card-meta span {
  background: rgba(127, 139, 184, 0.2);
  color: var(--text);
}

.card--hero {
  margin-bottom: 20px;
}

.card--compact {
  padding: 22px;
}

.card--compact h3 {
  font-size: 1.05rem;
  margin-bottom: 8px;
}

.card--compact p {
  font-size: 0.9rem;
  color: var(--text-dim);
  margin-bottom: 14px;
}

.card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 14px;
}

.card-badge {
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  background: var(--accent-glow);
  padding: 4px 12px;
  border-radius: 100px;
}

.card-badge.badge--star {
  color: var(--green);
  background: rgba(74, 222, 128, 0.12);
}

.card-links {
  display: flex;
  gap: 16px;
}

.card-links a {
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--text-muted);
  transition: color 0.2s;
}

.card-links a:hover { color: var(--accent); }

.card h3 {
  font-size: 1.4rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 4px;
}

.card h3 a {
  color: var(--text);
  transition: color 0.2s;
}

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

.card-tagline {
  color: var(--text-dim);
  font-size: 0.95rem;
  margin-bottom: 6px;
}

.card-meta {
  display: flex;
  gap: 12px;
  margin-bottom: 10px;
}

.card-meta span {
  font-size: 0.75rem;
  color: var(--text-muted);
  background: rgba(255,255,255,0.04);
  padding: 2px 8px;
  border-radius: 4px;
}

.meta-stars {
  color: var(--amber, #fbbf24) !important;
}

.card > p {
  color: var(--text-dim);
  font-size: 0.92rem;
  line-height: 1.6;
  margin-bottom: 20px;
}

/* Card features grid */
.card-features {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
  margin-bottom: 20px;
}

.feature strong {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 2px;
}

.feature span {
  font-size: 0.8rem;
  color: var(--text-muted);
  line-height: 1.4;
}

.feature span a, .card > p a, .feature-list a, .knowledge-card p a {
  color: var(--accent-dim);
  text-decoration: underline;
  text-decoration-color: var(--border-light);
  text-underline-offset: 2px;
}

.feature span a:hover, .card > p a:hover, .feature-list a:hover, .knowledge-card p a:hover {
  color: var(--accent);
}

.section-desc a {
  color: var(--accent-dim);
  text-decoration: underline;
  text-decoration-color: var(--border-light);
  text-underline-offset: 2px;
}

.section-desc a:hover {
  color: var(--accent);
}

/* Feature list (bullets) */
.feature-list {
  list-style: none;
  margin-bottom: 20px;
}

.feature-list li {
  position: relative;
  padding-left: 18px;
  font-size: 0.88rem;
  color: var(--text-dim);
  margin-bottom: 6px;
}

.feature-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 8px;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--accent-dim);
}

/* Tech tags */
.card-tech {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.card-tech span {
  font-size: 0.72rem;
  font-weight: 500;
  padding: 3px 10px;
  border-radius: 100px;
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--border);
  color: var(--text-muted);
}

/* Card grids */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 26px;
}

.card-grid--3 {
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.link-card {
  background: linear-gradient(180deg, rgba(18, 24, 43, 0.9), rgba(20, 28, 52, 0.95));
  border: 1px solid var(--border);
  padding: 24px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.24);
}

.link-card:hover {
  border-color: var(--accent-dim);
  box-shadow: 0 10px 20px rgba(23, 33, 70, 0.45);
}

/* ===== Subsection titles ===== */
.subsection-title {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--text);
  margin-top: 40px;
  margin-bottom: 16px;
  letter-spacing: -0.01em;
}

/* ===== Link grid (external resources) ===== */
.link-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 14px;
  margin-bottom: 20px;
}

.link-card {
  padding: 20px;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border);
  transition: border-color 0.25s;
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.5s ease, transform 0.5s ease, border-color 0.25s;
}

.link-card.visible {
  opacity: 1;
  transform: translateY(0);
}

.link-card:hover {
  border-color: var(--border-light);
}

.link-card-header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 10px;
  margin-bottom: 4px;
}

.link-card-header .card-links {
  flex-shrink: 0;
  gap: 10px;
}

.link-card-header .card-links a {
  font-size: 0.72rem;
}

.link-card h4 {
  font-size: 0.92rem;
  font-weight: 600;
  margin-bottom: 0;
}

.link-card h4 a {
  color: var(--accent);
}

.link-card .card-meta {
  margin-bottom: 6px;
}

.link-card .card-meta span {
  font-size: 0.68rem;
  padding: 1px 6px;
}

.link-card p {
  font-size: 0.82rem;
  color: var(--text-muted);
  line-height: 1.55;
  margin-bottom: 10px;
}

.link-card p a {
  color: var(--text-dim);
  text-decoration: underline;
  text-decoration-color: var(--border-light);
  text-underline-offset: 2px;
}

.link-card p a:hover {
  color: var(--accent);
}

/* ===== Knowledge cards ===== */
.knowledge-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 20px;
}

.knowledge-card {
  padding: 28px;
  border-radius: var(--radius);
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid var(--border);
  transition: border-color 0.25s;
}

.knowledge-card:hover {
  border-color: var(--border-light);
}

.knowledge-card h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 10px;
  color: var(--text);
}

.knowledge-card p {
  font-size: 0.88rem;
  color: var(--text-dim);
  line-height: 1.65;
}

/* ===== Subsection descriptions ===== */
.subsection-desc {
  color: var(--text-muted);
  font-size: 0.92rem;
  margin-bottom: 20px;
  max-width: 600px;
  line-height: 1.55;
}

.subsection-desc a {
  color: var(--accent-dim);
  text-decoration: underline;
  text-decoration-color: var(--border-light);
  text-underline-offset: 2px;
}

.subsection-desc a:hover {
  color: var(--accent);
}

/* ===== Footer ===== */
.site-footer {
  padding: 40px 0;
  border-top: 1px solid var(--border);
  text-align: center;
}

.site-footer p {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* ===== Animations ===== */
.card, .knowledge-card {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.5s ease, transform 0.5s ease, border-color 0.25s, box-shadow 0.25s;
}

.card.visible, .knowledge-card.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .hero { padding: 80px 0 60px; }
  .section { padding: 60px 0; }
  .card-features { grid-template-columns: 1fr; }
  .card-grid { grid-template-columns: 1fr; }
  .card-grid--3 { grid-template-columns: 1fr; }
  .knowledge-grid { grid-template-columns: 1fr; }
  .link-grid { grid-template-columns: 1fr; }
}

@media (max-width: 480px) {
  .hero h1 { font-size: 2.2rem; }
  .hero-nav { gap: 6px; }
  .hero-nav a { padding: 6px 14px; font-size: 0.8rem; }
  .card { padding: 20px; }
}