/* =========================================================
   LearnFutureTech — Design System
   ========================================================= */

/* ---------- Theme tokens ---------- */
:root {
  --bg: #f7f8fb;
  --bg-elev: #ffffff;
  --bg-soft: #eef1f7;
  --text: #11151c;
  --text-muted: #5b6675;
  --border: #e3e8f0;
  --brand: #6d28d9;
  --brand-2: #2563eb;
  --accent: #06b6d4;
  --shadow: 0 10px 30px -12px rgba(20, 30, 60, 0.18);
  --shadow-sm: 0 4px 14px -8px rgba(20, 30, 60, 0.25);
  --radius: 16px;
  --radius-sm: 10px;
  --maxw: 1160px;
  --header-h: 68px;
  --grad: linear-gradient(135deg, #6d28d9 0%, #2563eb 50%, #06b6d4 100%);
  --font: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

:root[data-theme="dark"] {
  --bg: #0b0e14;
  --bg-elev: #131822;
  --bg-soft: #1a2130;
  --text: #eaf0f8;
  --text-muted: #97a3b6;
  --border: #232c3b;
  --brand: #a78bfa;
  --brand-2: #60a5fa;
  --accent: #22d3ee;
  --shadow: 0 16px 40px -18px rgba(0, 0, 0, 0.7);
  --shadow-sm: 0 6px 18px -10px rgba(0, 0, 0, 0.6);
  --grad: linear-gradient(135deg, #a78bfa 0%, #60a5fa 50%, #22d3ee 100%);
}

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

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  transition: background 0.3s ease, color 0.3s ease;
}

img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }

h1, h2, h3, h4 { line-height: 1.2; font-weight: 700; letter-spacing: -0.02em; }

.container {
  width: 100%;
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 22px;
}

.gradient-text {
  background: var(--grad);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.muted { color: var(--text-muted); }
.center { text-align: center; }

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 22px;
  border-radius: 999px;
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  border: 1px solid transparent;
  transition: transform 0.15s ease, box-shadow 0.2s ease, background 0.2s ease;
  white-space: nowrap;
}
.btn:active { transform: translateY(1px) scale(0.99); }

.btn-primary {
  background: var(--grad);
  color: #fff;
  box-shadow: var(--shadow-sm);
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: var(--shadow); }

.btn-ghost {
  background: var(--bg-elev);
  color: var(--text);
  border-color: var(--border);
}
.btn-ghost:hover { border-color: var(--brand); color: var(--brand); }

/* ---------- Header / Nav ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--header-h);
  display: flex;
  align-items: center;
  background: color-mix(in srgb, var(--bg-elev) 82%, transparent);
  backdrop-filter: saturate(160%) blur(14px);
  border-bottom: 1px solid var(--border);
}
.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  font-size: 1.15rem;
  letter-spacing: -0.03em;
}
.brand .logo-mark {
  width: 34px;
  height: 34px;
  border-radius: 10px;
  background: var(--grad);
  display: grid;
  place-items: center;
  color: #fff;
  font-size: 18px;
  box-shadow: var(--shadow-sm);
}
.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-links a {
  padding: 9px 14px;
  border-radius: 10px;
  font-weight: 500;
  color: var(--text-muted);
  transition: color 0.15s, background 0.15s;
}
.nav-links a:hover { color: var(--text); background: var(--bg-soft); }
.nav-links a.active { color: var(--brand); background: var(--bg-soft); }

.nav-actions { display: flex; align-items: center; gap: 10px; }

.theme-toggle {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 1px solid var(--border);
  background: var(--bg-elev);
  color: var(--text);
  cursor: pointer;
  display: grid;
  place-items: center;
  font-size: 18px;
  transition: transform 0.2s, border-color 0.2s;
}
.theme-toggle:hover { transform: rotate(15deg); border-color: var(--brand); }

.hamburger {
  display: none;
  width: 42px;
  height: 42px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--bg-elev);
  cursor: pointer;
  color: var(--text);
}

/* ---------- Hero ---------- */
.hero {
  position: relative;
  overflow: hidden;
  padding: 84px 0 64px;
}
.hero-grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 48px;
  align-items: center;
}
.hero .eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 14px;
  border-radius: 999px;
  background: var(--bg-soft);
  border: 1px solid var(--border);
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--brand);
  margin-bottom: 18px;
}
.hero h1 {
  font-size: clamp(2.2rem, 5vw, 3.6rem);
  margin: 0 0 18px;
}
.hero p.lead {
  font-size: 1.15rem;
  color: var(--text-muted);
  max-width: 540px;
  margin: 0 0 28px;
}
.hero-cta { display: flex; gap: 12px; flex-wrap: wrap; }

/* search bar in hero */
.hero-search {
  margin-top: 28px;
  display: flex;
  gap: 10px;
  max-width: 480px;
}
.hero-search input {
  flex: 1;
  padding: 13px 18px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--bg-elev);
  color: var(--text);
  font-size: 0.95rem;
  font-family: inherit;
}
.hero-search input:focus { outline: 2px solid var(--brand); outline-offset: 1px; }

/* animated visual */
.hero-visual {
  position: relative;
  aspect-ratio: 1 / 1;
  display: grid;
  place-items: center;
}
.orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(2px);
  background: var(--grad);
  opacity: 0.85;
  animation: float 7s ease-in-out infinite;
}
.orb.o1 { width: 60%; height: 60%; opacity: 0.18; filter: blur(40px); }
.hero-card {
  position: relative;
  width: 78%;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 22px;
  padding: 22px;
  box-shadow: var(--shadow);
  animation: float 6s ease-in-out infinite;
}
.hero-card .chip {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 8px;
}
.hero-card h4 { margin: 0 0 10px; font-size: 1.05rem; }
.hero-card .bar { height: 8px; border-radius: 6px; background: var(--bg-soft); overflow: hidden; margin: 6px 0; }
.hero-card .bar span { display: block; height: 100%; background: var(--grad); border-radius: 6px; animation: grow 2.4s ease forwards; }

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-14px); }
}
@keyframes grow { from { width: 0; } }

/* ---------- Section helpers ---------- */
.section { padding: 64px 0; }
.section-head {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 30px;
  flex-wrap: wrap;
}
.section-head h2 { font-size: clamp(1.6rem, 3vw, 2.2rem); margin: 0; }
.section-head p { margin: 6px 0 0; color: var(--text-muted); }
.link-arrow { color: var(--brand); font-weight: 600; }
.link-arrow:hover { text-decoration: underline; }

/* ---------- Stats ---------- */
.stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 18px;
}
.stat {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 26px 20px;
  text-align: center;
  box-shadow: var(--shadow-sm);
}
.stat .num { font-size: 2.2rem; font-weight: 800; }
.stat .label { color: var(--text-muted); font-size: 0.9rem; margin-top: 4px; }

/* ---------- Category explorer ---------- */
.cat-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
}
.cat-card {
  position: relative;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 26px;
  cursor: pointer;
  overflow: hidden;
  transition: transform 0.2s, box-shadow 0.2s, border-color 0.2s;
}
.cat-card:hover { transform: translateY(-4px); box-shadow: var(--shadow); border-color: transparent; }
.cat-card .cat-icon {
  width: 52px; height: 52px;
  border-radius: 14px;
  display: grid; place-items: center;
  font-size: 24px;
  background: var(--bg-soft);
  margin-bottom: 14px;
}
.cat-card h3 { margin: 0 0 6px; font-size: 1.15rem; }
.cat-card p { margin: 0; color: var(--text-muted); font-size: 0.92rem; }
.cat-card .count { margin-top: 14px; font-size: 0.82rem; font-weight: 600; color: var(--brand); }

/* ---------- Article cards ---------- */
.card-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}
.post-card {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: transform 0.2s, box-shadow 0.2s;
}
.post-card:hover { transform: translateY(-5px); box-shadow: var(--shadow); }
.post-card .thumb {
  aspect-ratio: 16 / 9;
  display: grid;
  place-items: center;
  font-size: 46px;
  color: #fff;
  position: relative;
}
.post-card .thumb .tag {
  position: absolute;
  top: 12px; left: 12px;
  background: rgba(0,0,0,0.35);
  backdrop-filter: blur(4px);
  color: #fff;
  font-size: 0.72rem;
  font-weight: 600;
  padding: 4px 10px;
  border-radius: 999px;
}
.post-card .body { padding: 20px; display: flex; flex-direction: column; flex: 1; }
.post-card h3 { margin: 0 0 8px; font-size: 1.15rem; }
.post-card .excerpt { color: var(--text-muted); font-size: 0.92rem; margin: 0 0 16px; flex: 1; }
.post-meta {
  display: flex; align-items: center; gap: 10px;
  font-size: 0.82rem; color: var(--text-muted);
}
.post-meta .dot { opacity: 0.5; }

/* ---------- Filter tabs ---------- */
.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 28px;
}
.filter-tab {
  padding: 9px 18px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--bg-elev);
  color: var(--text-muted);
  font-weight: 600;
  font-size: 0.88rem;
  cursor: pointer;
  transition: all 0.15s;
}
.filter-tab:hover { color: var(--text); }
.filter-tab.active { background: var(--grad); color: #fff; border-color: transparent; }

.search-row {
  display: flex;
  gap: 12px;
  margin-bottom: 22px;
  flex-wrap: wrap;
}
.search-row input {
  flex: 1;
  min-width: 220px;
  padding: 13px 18px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--bg-elev);
  color: var(--text);
  font-size: 0.95rem;
  font-family: inherit;
}
.search-row input:focus { outline: 2px solid var(--brand); outline-offset: 1px; }

.no-results {
  text-align: center;
  padding: 60px 20px;
  color: var(--text-muted);
}

/* ---------- Newsletter ---------- */
.newsletter {
  background: var(--grad);
  border-radius: 24px;
  padding: 48px;
  text-align: center;
  color: #fff;
  position: relative;
  overflow: hidden;
}
.newsletter h2 { font-size: clamp(1.6rem, 3vw, 2.2rem); margin: 0 0 10px; color: #fff; }
.newsletter p { opacity: 0.92; max-width: 520px; margin: 0 auto 24px; }
.newsletter form {
  display: flex;
  gap: 10px;
  max-width: 460px;
  margin: 0 auto;
}
.newsletter input {
  flex: 1;
  padding: 13px 18px;
  border-radius: 999px;
  border: none;
  font-size: 0.95rem;
  font-family: inherit;
}
.newsletter input:focus { outline: 3px solid rgba(255,255,255,0.5); }
.newsletter .btn {
  background: #0b0e14;
  color: #fff;
}
.newsletter .form-msg { margin-top: 14px; font-weight: 600; min-height: 22px; }

/* ---------- Article (single) ---------- */
.progress-bar {
  position: fixed;
  top: 0; left: 0;
  height: 3px;
  width: 0;
  background: var(--grad);
  z-index: 100;
  transition: width 0.1s linear;
}
.article-head { padding: 48px 0 24px; }
.article-head .tag-pill {
  display: inline-block;
  background: var(--bg-soft);
  color: var(--brand);
  font-weight: 600;
  font-size: 0.82rem;
  padding: 5px 14px;
  border-radius: 999px;
  margin-bottom: 16px;
}
.article-head h1 { font-size: clamp(2rem, 4.5vw, 3rem); margin: 0 0 16px; max-width: 820px; }
.article-byline {
  display: flex; align-items: center; gap: 12px;
  color: var(--text-muted); font-size: 0.92rem;
}
.avatar {
  width: 42px; height: 42px; border-radius: 50%;
  background: var(--grad); color: #fff;
  display: grid; place-items: center; font-weight: 700;
}
.article-cover {
  aspect-ratio: 21 / 9;
  border-radius: 20px;
  display: grid; place-items: center;
  font-size: 70px; color: #fff;
  margin: 8px 0 36px;
}
.article-body {
  max-width: 760px;
  margin: 0 auto;
  font-size: 1.08rem;
}
.article-body h2 { font-size: 1.6rem; margin: 38px 0 14px; }
.article-body h3 { font-size: 1.25rem; margin: 28px 0 10px; }
.article-body p { margin: 0 0 20px; color: var(--text); }
.article-body ul, .article-body ol { margin: 0 0 20px; padding-left: 22px; color: var(--text); }
.article-body li { margin-bottom: 8px; }
.article-body blockquote {
  margin: 24px 0;
  padding: 16px 22px;
  border-left: 4px solid var(--brand);
  background: var(--bg-soft);
  border-radius: 0 12px 12px 0;
  font-style: italic;
  color: var(--text);
}
.article-body code {
  background: var(--bg-soft);
  padding: 2px 7px;
  border-radius: 6px;
  font-size: 0.9em;
}
.share-row {
  display: flex; align-items: center; gap: 10px;
  margin: 36px 0;
  padding: 20px 0;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}
.share-row span { font-weight: 600; margin-right: 6px; }
.share-btn {
  width: 42px; height: 42px; border-radius: 50%;
  border: 1px solid var(--border);
  background: var(--bg-elev);
  cursor: pointer;
  display: grid; place-items: center;
  color: var(--text);
  transition: all 0.15s;
}
.share-btn:hover { background: var(--grad); color: #fff; border-color: transparent; }

/* ---------- About page ---------- */
.about-hero { padding: 64px 0 32px; text-align: center; }
.about-hero h1 { font-size: clamp(2rem, 4vw, 3rem); margin: 0 0 14px; }
.about-hero p { max-width: 640px; margin: 0 auto; color: var(--text-muted); font-size: 1.1rem; }
.values {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
.value-card {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 26px;
}
.value-card .v-icon { font-size: 30px; margin-bottom: 12px; }
.value-card h3 { margin: 0 0 8px; }
.value-card p { margin: 0; color: var(--text-muted); font-size: 0.94rem; }

/* ---------- Footer ---------- */
.site-footer {
  margin-top: 40px;
  border-top: 1px solid var(--border);
  background: var(--bg-elev);
  padding: 48px 0 28px;
}
.footer-grid {
  display: grid;
  grid-template-columns: 1.6fr 1fr 1fr 1fr;
  gap: 28px;
  margin-bottom: 32px;
}
.footer-grid h4 { font-size: 0.95rem; margin: 0 0 14px; }
.footer-grid ul { list-style: none; padding: 0; margin: 0; }
.footer-grid li { margin-bottom: 10px; }
.footer-grid a { color: var(--text-muted); font-size: 0.92rem; }
.footer-grid a:hover { color: var(--brand); }
.footer-grid p { color: var(--text-muted); font-size: 0.92rem; max-width: 280px; }
.footer-bottom {
  display: flex; justify-content: space-between; align-items: center;
  padding-top: 22px;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.86rem;
  flex-wrap: wrap;
  gap: 12px;
}
.social-row { display: flex; gap: 10px; }
.social-row a {
  width: 38px; height: 38px; border-radius: 50%;
  border: 1px solid var(--border);
  display: grid; place-items: center;
  color: var(--text-muted);
  transition: all 0.15s;
}
.social-row a:hover { background: var(--grad); color: #fff; border-color: transparent; }

/* ---------- Reveal on scroll ---------- */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.reveal.in { opacity: 1; transform: none; }

/* ---------- Toast ---------- */
.toast {
  position: fixed;
  bottom: 24px; left: 50%;
  transform: translateX(-50%) translateY(120%);
  background: var(--text);
  color: var(--bg);
  padding: 12px 22px;
  border-radius: 999px;
  font-weight: 600;
  font-size: 0.9rem;
  box-shadow: var(--shadow);
  z-index: 200;
  transition: transform 0.3s ease;
}
.toast.show { transform: translateX(-50%) translateY(0); }

/* ---------- Responsive ---------- */
@media (max-width: 900px) {
  .hero-grid { grid-template-columns: 1fr; }
  .hero-visual { display: none; }
  .cat-grid, .card-grid, .values { grid-template-columns: repeat(2, 1fr); }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 640px) {
  .nav-links {
    position: fixed;
    top: var(--header-h);
    left: 0; right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background: var(--bg-elev);
    border-bottom: 1px solid var(--border);
    padding: 10px 14px 18px;
    transform: translateY(-150%);
    transition: transform 0.3s ease;
    box-shadow: var(--shadow);
  }
  .nav-links.open { transform: translateY(0); }
  .nav-links a { padding: 13px 14px; border-radius: 10px; }
  .hamburger { display: grid; place-items: center; }
  .cat-grid, .card-grid, .values, .stats { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
  .newsletter { padding: 32px 20px; }
  .newsletter form, .hero-search, .search-row { flex-direction: column; }
  .newsletter input, .newsletter .btn { width: 100%; }
  .section { padding: 48px 0; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
  html { scroll-behavior: auto; }
}