:root {
  --bg: #0a0a0f;
  --bg-soft: #12121a;
  --bg-card: #16161f;
  --border: #26262f;
  --text: #e7e7ee;
  --muted: #9a9ab0;
  --accent: #7c5cff;
  --accent-2: #21d4fd;
  --accent-grad: linear-gradient(120deg, #7c5cff 0%, #21d4fd 100%);
  --green: #34d399;
  --radius: 16px;
  --maxw: 920px;
}

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

html { scroll-behavior: smooth; }

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

a { color: var(--accent-2); text-decoration: none; }
a:hover { text-decoration: underline; }

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

/* ===== Top nav ===== */
.nav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(10,10,15,.72);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
}
.nav-inner {
  max-width: 1100px; margin: 0 auto; padding: 14px 22px;
  display: flex; align-items: center; justify-content: space-between;
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 18px; letter-spacing: -.02em; color: var(--text); }
.brand .dot { width: 12px; height: 12px; border-radius: 50%; background: var(--accent-grad); box-shadow: 0 0 16px var(--accent); }
.brand:hover { text-decoration: none; }
.nav-links { display: flex; gap: 22px; align-items: center; }
.nav-links a { color: var(--muted); font-size: 15px; font-weight: 500; }
.nav-links a:hover { color: var(--text); text-decoration: none; }
.nav-cta { background: var(--accent-grad); color: #fff !important; padding: 9px 18px; border-radius: 999px; font-weight: 600; }

/* ===== Hero ===== */
.hero { position: relative; padding: 96px 0 70px; text-align: center; overflow: hidden; }
.hero::before {
  content: ""; position: absolute; inset: 0;
  background: radial-gradient(700px 380px at 50% -10%, rgba(124,92,255,.22), transparent 60%),
              radial-gradient(500px 300px at 80% 10%, rgba(33,212,253,.14), transparent 60%);
  pointer-events: none;
}
.hero-badge {
  display: inline-flex; align-items: center; gap: 8px;
  background: var(--bg-card); border: 1px solid var(--border);
  padding: 7px 16px; border-radius: 999px; font-size: 14px; color: var(--muted); margin-bottom: 26px;
}
.hero-badge b { color: var(--accent-2); }
.hero h1 {
  font-size: clamp(38px, 6vw, 66px); line-height: 1.04; letter-spacing: -.03em; font-weight: 800;
}
.hero h1 .grad { background: var(--accent-grad); -webkit-background-clip: text; background-clip: text; color: transparent; }
.hero p.lead { max-width: 640px; margin: 24px auto 0; font-size: 19px; color: var(--muted); }
.hero-actions { margin-top: 38px; display: flex; gap: 14px; justify-content: center; flex-wrap: wrap; }

.btn {
  display: inline-flex; align-items: center; gap: 9px;
  padding: 14px 28px; border-radius: 999px; font-weight: 600; font-size: 16px; cursor: pointer;
  transition: transform .15s ease, box-shadow .15s ease;
}
.btn-primary { background: var(--accent-grad); color: #fff; box-shadow: 0 10px 30px rgba(124,92,255,.32); }
.btn-primary:hover { transform: translateY(-2px); text-decoration: none; box-shadow: 0 14px 38px rgba(124,92,255,.45); }
.btn-ghost { background: var(--bg-card); border: 1px solid var(--border); color: var(--text); }
.btn-ghost:hover { border-color: var(--accent); text-decoration: none; }

.hero-stats { margin-top: 56px; display: flex; gap: 46px; justify-content: center; flex-wrap: wrap; }
.hero-stats .stat b { display: block; font-size: 30px; font-weight: 800; background: var(--accent-grad); -webkit-background-clip: text; background-clip: text; color: transparent; }
.hero-stats .stat span { font-size: 14px; color: var(--muted); }

/* ===== Sections ===== */
.section { padding: 70px 0; }
.section-head { text-align: center; margin-bottom: 48px; }
.section-head h2 { font-size: clamp(28px,4vw,40px); letter-spacing: -.02em; font-weight: 800; }
.section-head p { color: var(--muted); margin-top: 12px; font-size: 17px; }
.eyebrow { color: var(--accent-2); font-weight: 700; font-size: 14px; text-transform: uppercase; letter-spacing: .08em; }

/* ===== Feature grid ===== */
.features { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.feature { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 26px; }
.feature .ico { font-size: 28px; margin-bottom: 14px; }
.feature h3 { font-size: 18px; margin-bottom: 8px; }
.feature p { color: var(--muted); font-size: 15px; }

/* ===== Lesson cards ===== */
.lessons-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 16px; }
.lcard {
  position: relative; display: block; background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 24px; transition: border-color .15s ease, transform .15s ease;
}
.lcard:hover { border-color: var(--accent); transform: translateY(-3px); text-decoration: none; }
.lcard .num { font-size: 13px; font-weight: 700; color: var(--accent-2); letter-spacing: .05em; }
.lcard h3 { font-size: 19px; margin: 8px 0 8px; color: var(--text); letter-spacing: -.01em; }
.lcard p { color: var(--muted); font-size: 14.5px; }
.lcard .tags { margin-top: 16px; display: flex; gap: 7px; flex-wrap: wrap; }
.lcard .tag { font-size: 12px; color: var(--muted); background: var(--bg-soft); border: 1px solid var(--border); padding: 4px 10px; border-radius: 999px; }
.lcard .done-badge { position: absolute; top: 20px; right: 20px; width: 26px; height: 26px; border-radius: 50%; background: var(--green); color: #04130c; display: none; align-items: center; justify-content: center; font-size: 15px; font-weight: 700; }
.lcard.done .done-badge { display: flex; }
.lcard.done { border-color: rgba(52,211,153,.4); }

/* ===== CTA band ===== */
.cta-band { background: var(--bg-soft); border: 1px solid var(--border); border-radius: 22px; padding: 54px 40px; text-align: center; }
.cta-band h2 { font-size: 32px; letter-spacing: -.02em; }
.cta-band p { color: var(--muted); margin: 14px auto 28px; max-width: 520px; }

/* ===== Footer ===== */
.footer { border-top: 1px solid var(--border); padding: 40px 0; color: var(--muted); font-size: 14px; }
.footer-inner { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 16px; }

/* ===== Lesson page ===== */
.lesson-wrap { max-width: var(--maxw); margin: 0 auto; padding: 50px 22px 80px; }
.lesson-progress-bar { position: fixed; top: 0; left: 0; height: 3px; background: var(--accent-grad); z-index: 60; width: 0; transition: width .1s linear; }
.crumb { color: var(--muted); font-size: 14px; margin-bottom: 18px; }
.lesson-head { border-bottom: 1px solid var(--border); padding-bottom: 30px; margin-bottom: 36px; }
.lesson-head .num { color: var(--accent-2); font-weight: 700; letter-spacing: .06em; font-size: 14px; }
.lesson-head h1 { font-size: clamp(30px,5vw,46px); letter-spacing: -.02em; margin: 10px 0 14px; line-height: 1.1; }
.lesson-head .sub { color: var(--muted); font-size: 18px; }
.lesson-meta { display: flex; gap: 18px; margin-top: 20px; color: var(--muted); font-size: 14px; flex-wrap: wrap; }

.lesson-body h2 { font-size: 27px; margin: 44px 0 16px; letter-spacing: -.01em; scroll-margin-top: 80px; }
.lesson-body h3 { font-size: 20px; margin: 30px 0 12px; }
.lesson-body p { margin: 14px 0; color: #d4d4e0; }
.lesson-body ul, .lesson-body ol { margin: 14px 0 14px 24px; color: #d4d4e0; }
.lesson-body li { margin: 7px 0; }
.lesson-body strong { color: #fff; }
.lesson-body code:not(pre code) { background: var(--bg-soft); border: 1px solid var(--border); padding: 2px 7px; border-radius: 6px; font-size: 14px; font-family: 'JetBrains Mono', monospace; color: var(--accent-2); }

.objectives { background: linear-gradient(135deg, rgba(124,92,255,.10), rgba(33,212,253,.06)); border: 1px solid var(--border); border-radius: var(--radius); padding: 24px 26px; margin: 28px 0; }
.objectives h3 { margin: 0 0 12px; font-size: 17px; color: var(--accent-2); }
.objectives ul { margin: 0 0 0 20px; }

.callout { display: flex; gap: 14px; background: var(--bg-card); border: 1px solid var(--border); border-left: 3px solid var(--accent); border-radius: 12px; padding: 16px 18px; margin: 22px 0; }
.callout.tip { border-left-color: var(--green); }
.callout.warn { border-left-color: #fbbf24; }
.callout .c-ico { font-size: 20px; }
.callout p { margin: 0; font-size: 15px; }

pre[class*="language-"] { border-radius: 12px !important; border: 1px solid var(--border); margin: 20px 0 !important; font-size: 14px !important; }
:not(pre) > code[class*="language-"], pre[class*="language-"] { background: #0d0d14 !important; }
.code-label { font-family: 'JetBrains Mono', monospace; font-size: 12px; color: var(--muted); margin: 22px 0 -10px; text-transform: uppercase; letter-spacing: .05em; }

.task-box { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 26px; margin: 36px 0; }
.task-box h3 { margin: 0 0 6px; display: flex; align-items: center; gap: 10px; }
.task-box .label { font-size: 13px; color: var(--accent-2); font-weight: 700; text-transform: uppercase; letter-spacing: .06em; }

.checklist { list-style: none; margin-left: 0 !important; }
.checklist li { display: flex; gap: 10px; align-items: flex-start; margin: 9px 0; }
.checklist li::before { content: "✓"; color: var(--green); font-weight: 700; }

/* lesson nav */
.lesson-nav { display: flex; justify-content: space-between; gap: 16px; margin-top: 50px; padding-top: 30px; border-top: 1px solid var(--border); }
.lesson-nav a { flex: 1; background: var(--bg-card); border: 1px solid var(--border); border-radius: 12px; padding: 16px 20px; color: var(--text); transition: border-color .15s; }
.lesson-nav a:hover { border-color: var(--accent); text-decoration: none; }
.lesson-nav a.next { text-align: right; }
.lesson-nav a span { display: block; font-size: 12px; color: var(--muted); }
.lesson-nav a b { font-size: 15px; }
.lesson-nav a.disabled { opacity: .35; pointer-events: none; }

.complete-btn { width: 100%; margin-top: 30px; background: var(--bg-card); border: 1px solid var(--border); color: var(--text); padding: 16px; border-radius: 12px; font-weight: 600; font-size: 16px; cursor: pointer; transition: all .15s; }
.complete-btn:hover { border-color: var(--green); }
.complete-btn.done { background: rgba(52,211,153,.12); border-color: var(--green); color: var(--green); }

/* ===== Glossary ===== */
.glossary { display: grid; gap: 14px; margin: 24px 0; }
.term {
  background: var(--bg-card); border: 1px solid var(--border);
  border-left: 3px solid var(--accent); border-radius: 12px; padding: 18px 22px;
  scroll-margin-top: 80px;
}
.term h3 { margin: 0 0 6px; font-size: 18px; color: #fff; }
.term .aka { font-size: 13px; color: var(--accent-2); font-weight: 500; margin-left: 8px; }
.term p { margin: 0; color: #cfcfdc; font-size: 15px; }
.term p + p { margin-top: 8px; }
.term code { background: var(--bg-soft); border: 1px solid var(--border); padding: 1px 6px; border-radius: 5px; font-size: 13px; font-family: 'JetBrains Mono', monospace; color: var(--accent-2); }

.glossary-nav { display: flex; flex-wrap: wrap; gap: 7px; margin: 16px 0 26px; }
.glossary-nav a { font-size: 13px; color: var(--muted); background: var(--bg-soft); border: 1px solid var(--border); padding: 5px 12px; border-radius: 999px; }
.glossary-nav a:hover { color: var(--text); border-color: var(--accent); text-decoration: none; }

.gloss-search { position: relative; margin: 10px 0 20px; }
.gloss-search input {
  width: 100%; background: var(--bg-soft); border: 1px solid var(--border); border-radius: 12px;
  padding: 14px 18px 14px 46px; color: var(--text); font-size: 16px; font-family: inherit; outline: none;
}
.gloss-search input:focus { border-color: var(--accent); }
.gloss-search input::placeholder { color: var(--muted); }
.gloss-search::before { content: "🔍"; position: absolute; left: 16px; top: 50%; transform: translateY(-50%); font-size: 16px; opacity: .7; }
.gloss-empty { color: var(--muted); padding: 20px; text-align: center; display: none; }
.term.hidden, .glossary-nav a.hidden { display: none; }
mark { background: rgba(124,92,255,.35); color: #fff; border-radius: 3px; padding: 0 2px; }

/* lesson term links */
.lesson-terms { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 22px 24px; margin: 36px 0; }
.lesson-terms h3 { margin: 0 0 6px; font-size: 17px; }
.lesson-terms p.hint { margin: 0 0 14px; color: var(--muted); font-size: 14px; }
.lesson-terms .links { display: flex; flex-wrap: wrap; gap: 8px; }
.lesson-terms .links a { font-size: 14px; color: var(--accent-2); background: var(--bg-soft); border: 1px solid var(--border); padding: 6px 13px; border-radius: 999px; }
.lesson-terms .links a:hover { border-color: var(--accent); text-decoration: none; }

@media (max-width: 760px) {
  .features { grid-template-columns: 1fr; }
  .lessons-grid { grid-template-columns: 1fr; }
  .nav-links { display: none; }
  .hero-stats { gap: 28px; }
}