:root {
  --bg: #ffffff;
  --bg-alt: #f7f8fb;
  --surface: #ffffff;
  --border: #e6e8ef;
  --text: #0f1729;
  --text-2: #475467;
  --muted: #667085;
  --accent: #4f46e5;
  --accent-2: #7c3aed;
  --accent-hover: #4338ca;
  --accent-soft: #eef0ff;
  --ok: #3fb950;
  --bad: #f85149;
  --ed-bg: #0d1117;
  --ed-panel: #0a0d12;
  --ed-border: #21262d;
  --ed-text: #e6edf3;
  --ed-muted: #8b949e;
  --font: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --mono: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 80px; }
body { margin: 0; background: var(--bg); color: var(--text); font: 16px/1.6 var(--font); -webkit-font-smoothing: antialiased; }
img { display: block; max-width: 100%; height: auto; }
a { color: inherit; }
h1, h2, h3 { letter-spacing: -0.025em; line-height: 1.15; margin: 0; }
.wrap { max-width: 1160px; margin: 0 auto; padding: 0 24px; }
.narrow { max-width: 760px; }
.icon { width: 18px; height: 18px; fill: none; stroke: currentColor; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; }

/* syntax colors, same as the app */
.tk-str { color: #a5d6ff; }
.tk-fn { color: #d2a8ff; }

/* ---------- buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  height: 44px;
  padding: 0 18px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font-weight: 600;
  font-size: 15px;
  text-decoration: none;
  white-space: nowrap;
  transition: background 0.15s, border-color 0.15s, transform 0.05s, box-shadow 0.15s;
}
.btn:hover { background: var(--bg-alt); }
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; box-shadow: 0 6px 20px rgba(79, 70, 229, 0.28); }
.btn-primary:hover { background: var(--accent-hover); border-color: var(--accent-hover); }
.btn-lg { height: 52px; padding: 0 24px; font-size: 16px; border-radius: 14px; }
.btn-small { height: 38px; padding: 0 16px; font-size: 14px; border-radius: 10px; background: var(--text); border-color: var(--text); color: #fff; }
.btn-small:hover { background: #1f2a44; }
.btn-white { background: #fff; border-color: #fff; color: var(--accent); }
.btn-white:hover { background: #f1f1ff; }

/* ---------- nav ---------- */
.nav { position: sticky; top: 0; z-index: 10; background: rgba(255, 255, 255, 0.85); backdrop-filter: saturate(180%) blur(10px); border-bottom: 1px solid transparent; transition: border-color 0.2s; }
.nav-inner { display: flex; align-items: center; gap: 32px; height: 64px; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 700; font-size: 17px; text-decoration: none; }
.logo { display: grid; place-items: center; width: 32px; height: 32px; border-radius: 9px; background: linear-gradient(135deg, #6366f1, #4338ca); color: #fff; font: 700 13px/1 var(--mono); box-shadow: 0 2px 8px rgba(79, 70, 229, 0.35); }
.nav-links { display: flex; gap: 28px; margin-left: auto; }
.nav-links a { text-decoration: none; color: var(--text-2); font-size: 15px; font-weight: 500; }
.nav-links a:hover { color: var(--text); }

/* ---------- hero ---------- */
.hero {
  position: relative;
  overflow: hidden;
  padding: 72px 0 96px;
  background:
    radial-gradient(700px 400px at 85% 10%, rgba(124, 58, 237, 0.12), transparent 70%),
    radial-gradient(600px 400px at 10% 0%, rgba(79, 70, 229, 0.1), transparent 70%);
}
.hero-grid { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 56px; align-items: center; }
.pill { display: inline-block; padding: 6px 12px; border-radius: 99px; background: var(--accent-soft); color: var(--accent); font-size: 13px; font-weight: 600; margin-bottom: 20px; }
.hero h1 { font-size: clamp(34px, 4vw, 50px); font-weight: 800; letter-spacing: -0.035em; line-height: 1.05; margin-bottom: 20px; }
.grad { background: linear-gradient(90deg, var(--accent), var(--accent-2)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.lead { font-size: 19px; line-height: 1.6; color: var(--text-2); margin: 0 0 28px; max-width: 520px; }
.cta-row { display: flex; flex-wrap: wrap; gap: 12px; margin-bottom: 24px; }
.ticks { display: flex; flex-wrap: wrap; gap: 8px 20px; list-style: none; padding: 0; margin: 0; color: var(--text-2); font-size: 14px; }
.ticks li::before { content: "✓"; color: var(--accent); font-weight: 700; margin-right: 6px; }

.hero-shot { position: relative; padding-bottom: 40px; }
.browser { border-radius: 14px; overflow: hidden; border: 1px solid var(--border); background: #fff; box-shadow: 0 30px 80px rgba(15, 23, 41, 0.18), 0 8px 24px rgba(15, 23, 41, 0.08); transform: perspective(1600px) rotateY(-4deg) rotateX(2deg); transform-origin: left center; }
.browser-bar { display: flex; align-items: center; gap: 6px; height: 34px; padding: 0 12px; background: #f3f4f7; border-bottom: 1px solid var(--border); }
.browser-bar i { width: 10px; height: 10px; border-radius: 50%; background: #d8dbe3; }
.browser-bar span { margin-left: 12px; font-size: 12px; color: var(--muted); }
.phone {
  position: absolute;
  right: -12px;
  bottom: 0;
  width: 27%;
  padding: 6px;
  border-radius: 30px;
  background: #0b0d12;
  box-shadow: 0 24px 60px rgba(15, 23, 41, 0.35);
}
.phone img { border-radius: 24px; }

/* ---------- sections ---------- */
.section { padding: 96px 0; }
.section-alt { background: var(--bg-alt); }
.kicker { margin: 0 0 12px; font-size: 13px; font-weight: 700; letter-spacing: 0.08em; text-transform: uppercase; color: var(--accent); }
.section h2 { font-size: clamp(30px, 3.6vw, 42px); font-weight: 800; margin-bottom: 16px; }
.section-lead { font-size: 18px; color: var(--text-2); max-width: 680px; margin: 0 0 40px; }

.steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; margin-top: 40px; }
.step { padding: 28px; border-radius: 18px; background: var(--surface); border: 1px solid var(--border); }
.step-n { display: grid; place-items: center; width: 40px; height: 40px; border-radius: 12px; background: var(--accent-soft); color: var(--accent); font-weight: 800; margin-bottom: 18px; }
.step h3 { font-size: 20px; margin-bottom: 8px; }
.step p { margin: 0; color: var(--text-2); }

.features { display: grid; gap: 96px; }
.feature { display: grid; grid-template-columns: 1fr 1fr; gap: 64px; align-items: center; }
.feature.reverse .feature-copy { order: 2; }
.feature-copy p:not(.kicker) { font-size: 17px; color: var(--text-2); margin: 0; }

.mock { border-radius: 18px; padding: 22px; box-shadow: 0 20px 50px rgba(15, 23, 41, 0.12); }
.mock-dark { background: var(--ed-bg); color: var(--ed-text); border: 1px solid #1c2230; }
.mock-light { background: #fff; border: 1px solid var(--border); }
.mock-code { font: 14px/1.9 var(--mono); white-space: pre; overflow-x: auto; margin-bottom: 16px; }
.mock-code .ln { color: #484f58; display: inline-block; width: 24px; }
.mock-err { padding: 14px 16px; border-radius: 12px; background: rgba(248, 81, 73, 0.08); border: 1px solid rgba(248, 81, 73, 0.35); }
.err-title { font-weight: 600; color: #ffa198; margin-bottom: 6px; }
.err-title span { color: var(--ed-muted); font-weight: 500; }
.mock-err p { margin: 0 0 8px; font-size: 15px; }
.mock-err code { font: 12.5px var(--mono); color: var(--ed-muted); }

.mock-test { display: grid; grid-template-columns: 22px 1fr; align-items: center; gap: 10px; padding: 12px 14px; border-radius: 12px; border: 1px solid var(--ed-border); margin-bottom: 10px; background: var(--ed-panel); }
.mock-test:last-child { margin-bottom: 0; }
.mock-test .mark { display: grid; place-items: center; width: 22px; height: 22px; border-radius: 50%; font-size: 12px; font-weight: 800; }
.mock-test.ok .mark { background: rgba(63, 185, 80, 0.18); color: var(--ok); }
.mock-test.bad { border-color: rgba(248, 81, 73, 0.4); }
.mock-test.bad .mark { background: rgba(248, 81, 73, 0.18); color: var(--bad); }
.mock-test code { font: 14px var(--mono); }
.mock-cmp { grid-column: 2; display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin-top: 6px; }
.mock-cmp small { display: block; font-size: 11px; font-weight: 700; letter-spacing: 0.06em; text-transform: uppercase; color: var(--ed-muted); margin-bottom: 4px; }
.mock-cmp pre { margin: 0; padding: 8px 10px; border-radius: 8px; font: 13px var(--mono); background: var(--ed-bg); border: 1px solid rgba(63, 185, 80, 0.35); }
.mock-cmp div + div pre { border-color: rgba(248, 81, 73, 0.35); }

.mock-streak { font-size: 15px; color: var(--text-2); margin-bottom: 18px; }
.mock-streak strong { font-size: 28px; color: var(--text); margin-right: 6px; }
.mock-skill { display: grid; grid-template-columns: 1fr auto; font-size: 14px; margin-bottom: 14px; }
.mock-skill span:last-of-type { color: var(--muted); font-size: 13px; }
.mock-skill i { grid-column: 1 / -1; height: 7px; border-radius: 99px; margin-top: 6px; background: linear-gradient(90deg, #818cf8, #4f46e5) 0 0 / var(--w) 100% no-repeat, #eef0f5; }

.chapters { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; }
.chapter { padding: 28px; border-radius: 18px; border: 1px solid var(--border); background: var(--surface); }
.chapter header span { font-size: 13px; font-weight: 700; letter-spacing: 0.06em; text-transform: uppercase; color: var(--accent); }
.chapter h3 { font-size: 22px; margin: 4px 0 18px; }
.chapter ol { list-style: none; margin: 0; padding: 0; }
.chapter li { display: flex; align-items: center; gap: 14px; padding: 12px 0; border-top: 1px solid var(--border); font-weight: 500; }
.chapter li b { width: 28px; color: var(--muted); font-weight: 500; font-size: 14px; font-variant-numeric: tabular-nums; }
.chapter li em { margin-left: auto; font-style: normal; font-size: 12px; padding: 3px 9px; border-radius: 99px; background: var(--bg-alt); color: var(--text-2); }

.points { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; margin-top: 40px; }
.points article { padding: 24px; border-radius: 18px; background: var(--surface); border: 1px solid var(--border); }
.points h3 { font-size: 18px; margin-bottom: 8px; }
.points p { margin: 0; color: var(--text-2); font-size: 15px; }

.faq { margin-top: 32px; }
.faq details { border-bottom: 1px solid var(--border); }
.faq summary { display: flex; justify-content: space-between; align-items: center; gap: 16px; padding: 20px 0; font-size: 18px; font-weight: 600; cursor: pointer; list-style: none; }
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; font-size: 24px; font-weight: 400; color: var(--muted); transition: transform 0.2s; }
.faq details[open] summary::after { transform: rotate(45deg); }
.faq p { margin: 0 0 20px; color: var(--text-2); font-size: 16px; }

.final { padding: 88px 0; background: linear-gradient(135deg, #4f46e5, #6d28d9); color: #fff; text-align: center; }
.final h2 { font-size: clamp(30px, 4vw, 44px); font-weight: 800; margin-bottom: 12px; }
.final p { font-size: 18px; opacity: 0.85; margin: 0 0 28px; }

.footer { padding: 32px 0; border-top: 1px solid var(--border); }
.footer-inner { display: flex; align-items: center; gap: 24px; flex-wrap: wrap; }
.footer nav { display: flex; gap: 20px; margin-left: auto; }
.footer nav a { color: var(--text-2); text-decoration: none; font-size: 14px; }
.footer .copy { color: var(--muted); font-size: 14px; }

/* ---------- smaller screens ---------- */
@media (max-width: 980px) {
  .nav-links { display: none; }
  .nav-inner .btn-small { margin-left: auto; }
  .hero { padding: 48px 0 64px; }
  .hero-grid { grid-template-columns: 1fr; gap: 48px; }
  .browser { transform: none; }
  .steps, .points { grid-template-columns: 1fr 1fr; }
  .feature { grid-template-columns: 1fr; gap: 32px; }
  .feature.reverse .feature-copy { order: 0; }
  .features { gap: 72px; }
  .section { padding: 72px 0; }
}
@media (max-width: 640px) {
  .wrap { padding: 0 16px; }
  .lead { font-size: 17px; }
  .cta-row .btn { flex: 1; }
  .phone { width: 34%; right: -4px; }
  .steps, .points, .chapters { grid-template-columns: 1fr; }
  .mock-cmp { grid-template-columns: 1fr; }
  .footer nav { margin-left: 0; }
}