:root {
  --bg: #f5f7fb;
  --surface: #ffffff;
  --surface-soft: #eef3ff;
  --text: #152033;
  --muted: #5d6a7e;
  --line: #dbe2ee;
  --primary: #0b5fff;
  --primary-dark: #0848bd;
  --accent: #00a67e;
  --navy: #0d1b34;
  --shadow: 0 18px 50px rgba(24, 45, 80, .10);
  --radius: 20px;
  --container: 1180px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.65;
}
a { color: inherit; }
img { max-width: 100%; }
button, input { font: inherit; }

.skip-link {
  position: absolute;
  left: -9999px;
  top: 12px;
  z-index: 999;
  padding: .7rem 1rem;
  border-radius: 8px;
  background: var(--navy);
  color: white;
}
.skip-link:focus { left: 12px; }

.container { width: min(calc(100% - 32px), var(--container)); margin-inline: auto; }
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  border-bottom: 1px solid rgba(219, 226, 238, .85);
  background: rgba(255, 255, 255, .92);
  backdrop-filter: blur(14px);
}
.nav-wrap { min-height: 76px; display: flex; align-items: center; justify-content: space-between; gap: 24px; }
.brand { display: inline-flex; align-items: center; gap: 12px; text-decoration: none; }
.brand-mark {
  width: 42px;
  height: 42px;
  display: grid;
  place-items: center;
  border-radius: 12px;
  color: white;
  background: linear-gradient(135deg, var(--primary), #5c8cff);
  font-weight: 800;
  letter-spacing: -.04em;
}
.brand strong, .brand small { display: block; line-height: 1.2; }
.brand small { color: var(--muted); margin-top: 3px; }
.main-nav { display: flex; align-items: center; gap: 6px; }
.main-nav a { padding: .7rem .9rem; border-radius: 10px; text-decoration: none; color: var(--muted); font-weight: 650; }
.main-nav a:hover, .main-nav a.active { color: var(--primary); background: var(--surface-soft); }
.nav-toggle { display: none; border: 1px solid var(--line); background: white; border-radius: 10px; padding: .55rem .75rem; }

.hero {
  padding: 78px 0 66px;
  background:
    radial-gradient(circle at 85% 20%, rgba(11, 95, 255, .15), transparent 32%),
    radial-gradient(circle at 12% 80%, rgba(0, 166, 126, .10), transparent 26%),
    linear-gradient(180deg, #fff, #f5f7fb);
}
.hero-grid { display: grid; grid-template-columns: 1.25fr .75fr; align-items: center; gap: 54px; }
.eyebrow { margin: 0 0 12px; color: var(--primary); font-size: .82rem; font-weight: 800; letter-spacing: .1em; text-transform: uppercase; }
h1, h2, h3 { line-height: 1.15; letter-spacing: -.035em; }
h1 { margin: 0; font-size: clamp(2.6rem, 5.5vw, 5rem); max-width: 890px; }
h1 span { color: var(--primary); }
h2 { margin: 0 0 16px; font-size: clamp(2rem, 3.8vw, 3.35rem); }
h3 { margin: 0 0 10px; font-size: 1.28rem; }
.hero-copy { max-width: 720px; margin: 24px 0 0; color: var(--muted); font-size: 1.15rem; }
.hero-actions { display: flex; gap: 12px; flex-wrap: wrap; margin-top: 30px; }
.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: .8rem 1.15rem;
  border-radius: 12px;
  text-decoration: none;
  font-weight: 800;
  border: 1px solid transparent;
  cursor: pointer;
}
.button.primary { color: white; background: var(--primary); box-shadow: 0 10px 25px rgba(11, 95, 255, .24); }
.button.primary:hover { background: var(--primary-dark); }
.button.secondary { background: white; border-color: var(--line); }
.button.secondary:hover { border-color: var(--primary); color: var(--primary); }
.button.light { color: var(--navy); background: white; }
.hero-points { display: flex; gap: 18px; flex-wrap: wrap; padding: 0; margin: 26px 0 0; color: var(--muted); list-style: none; font-size: .92rem; }
.hero-points li::before { content: "✓"; margin-right: 7px; color: var(--accent); font-weight: 900; }
.hero-panel { padding: 28px; border: 1px solid rgba(219, 226, 238, .9); border-radius: 24px; background: rgba(255, 255, 255, .88); box-shadow: var(--shadow); }
.panel-head { display: flex; justify-content: space-between; gap: 16px; align-items: center; margin-bottom: 12px; }
.progress { height: 9px; overflow: hidden; border-radius: 999px; background: #e7ecf5; }
.progress span { display: block; width: 0; height: 100%; border-radius: inherit; background: linear-gradient(90deg, var(--primary), var(--accent)); transition: width .4s ease; }
.learning-cycle { padding: 0; margin: 24px 0 0; list-style: none; display: grid; gap: 16px; }
.learning-cycle li { display: flex; align-items: center; gap: 13px; }
.learning-cycle li > span { flex: 0 0 34px; width: 34px; height: 34px; display: grid; place-items: center; border-radius: 10px; background: var(--surface-soft); color: var(--primary); font-weight: 850; }
.learning-cycle strong, .learning-cycle small { display: block; }
.learning-cycle small { color: var(--muted); margin-top: 2px; }

.section { padding: 88px 0; }
.section-muted { background: white; border-block: 1px solid var(--line); }
.section-heading { max-width: 740px; margin-bottom: 38px; }
.section-heading > p:last-child { color: var(--muted); font-size: 1.05rem; }
.feature-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 18px; }
.feature-card { min-height: 230px; padding: 26px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); box-shadow: 0 8px 28px rgba(24, 45, 80, .05); }
.feature-number { display: inline-block; margin-bottom: 36px; color: var(--primary); font-weight: 900; }
.feature-card p { color: var(--muted); margin-bottom: 0; }
.split { display: grid; grid-template-columns: 1fr 1fr; align-items: center; gap: 58px; }
.check-list { padding: 0; margin: 24px 0; list-style: none; }
.check-list li { margin: 10px 0; }
.check-list li::before { content: "✓"; display: inline-grid; place-items: center; width: 22px; height: 22px; margin-right: 9px; border-radius: 50%; color: white; background: var(--accent); font-size: .75rem; font-weight: 900; }
.text-link { color: var(--primary); font-weight: 850; text-decoration: none; }
.code-card { overflow: hidden; border-radius: var(--radius); background: var(--navy); box-shadow: var(--shadow); }
.code-card-top { display: flex; gap: 7px; padding: 16px 18px; background: #132544; }
.code-card-top span { width: 10px; height: 10px; border-radius: 50%; background: #4e6488; }
.code-card pre { margin: 0; padding: 34px; color: #dce8ff; white-space: pre-wrap; font-size: 1.04rem; line-height: 1.9; }
.topic-grid { display: grid; grid-template-columns: repeat(5, 1fr); gap: 12px; }
.topic-grid a { min-height: 106px; display: flex; align-items: flex-end; padding: 18px; border: 1px solid var(--line); border-radius: 16px; background: white; text-decoration: none; font-weight: 800; }
.topic-grid a:hover { color: var(--primary); transform: translateY(-2px); box-shadow: 0 12px 25px rgba(24, 45, 80, .08); }
.cta-section { padding: 20px 0 90px; }
.cta-card { display: flex; align-items: center; justify-content: space-between; gap: 32px; padding: 42px; border-radius: 24px; color: white; background: linear-gradient(120deg, var(--primary-dark), var(--primary), #3d79ff); }
.cta-card h2 { margin-bottom: 0; max-width: 770px; }
.cta-card .eyebrow { color: #dce7ff; }

.page-hero { padding: 58px 0 42px; background: linear-gradient(180deg, white, var(--bg)); border-bottom: 1px solid var(--line); }
.page-hero p:last-child { max-width: 760px; color: var(--muted); font-size: 1.07rem; }
.content-layout { display: grid; grid-template-columns: 260px minmax(0, 1fr); gap: 42px; padding: 56px 0 90px; }
.sidebar { position: sticky; top: 100px; align-self: start; padding: 20px; border: 1px solid var(--line); border-radius: 16px; background: white; }
.sidebar strong { display: block; margin-bottom: 10px; }
.sidebar a { display: block; padding: .48rem .6rem; border-radius: 8px; color: var(--muted); text-decoration: none; font-size: .93rem; }
.sidebar a:hover { color: var(--primary); background: var(--surface-soft); }
.lesson { min-width: 0; }
.lesson section { scroll-margin-top: 105px; margin-bottom: 48px; }
.lesson p, .lesson li { color: #334057; }
.note, .warning, .success { margin: 24px 0; padding: 18px 20px; border-radius: 14px; border-left: 5px solid; }
.note { background: #eef4ff; border-color: var(--primary); }
.warning { background: #fff7e8; border-color: #e99a18; }
.success { background: #eafaf5; border-color: var(--accent); }
.table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: 14px; background: white; }
table { width: 100%; border-collapse: collapse; }
th, td { padding: .85rem 1rem; text-align: left; border-bottom: 1px solid var(--line); }
th { background: #f2f5fa; }
tr:last-child td { border-bottom: 0; }
.inline-code, code { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; }
.lesson-actions { display: flex; align-items: center; justify-content: space-between; gap: 18px; padding-top: 24px; border-top: 1px solid var(--line); }
.complete-control { display: flex; align-items: center; gap: 10px; font-weight: 750; }
.complete-control input { width: 20px; height: 20px; accent-color: var(--accent); }

.module-list { display: grid; gap: 18px; }
.module-card { padding: 24px; border: 1px solid var(--line); border-radius: 18px; background: white; }
.module-card header { display: flex; align-items: flex-start; justify-content: space-between; gap: 16px; }
.module-card p { color: var(--muted); }
.status { padding: .3rem .6rem; border-radius: 999px; background: #eef4ff; color: var(--primary); font-size: .78rem; font-weight: 850; white-space: nowrap; }
.status.ready { background: #e8f8f2; color: #08785e; }
.module-card ul { margin-bottom: 0; }

.quiz { display: grid; gap: 20px; }
.question-card { padding: 24px; border: 1px solid var(--line); border-radius: 18px; background: white; }
.question-card fieldset { border: 0; padding: 0; margin: 0; }
.question-card legend { margin-bottom: 14px; font-weight: 800; }
.option { display: flex; gap: 10px; align-items: flex-start; margin: 10px 0; padding: 12px; border-radius: 10px; background: #f7f9fc; }
.option input { margin-top: 5px; accent-color: var(--primary); }
.quiz-result { display: none; padding: 22px; border-radius: 14px; background: var(--navy); color: white; }
.quiz-result.show { display: block; }

.site-footer { padding: 42px 0; color: #c9d4e8; background: var(--navy); }
.footer-grid { display: grid; grid-template-columns: 1fr auto; gap: 32px; }
.site-footer p { max-width: 650px; color: #92a4c3; }
.site-footer a { display: block; color: #dbe6fa; text-decoration: none; margin: 4px 0; }

@media (max-width: 980px) {
  .hero-grid, .split { grid-template-columns: 1fr; }
  .feature-grid { grid-template-columns: repeat(2, 1fr); }
  .topic-grid { grid-template-columns: repeat(2, 1fr); }
  .content-layout { grid-template-columns: 1fr; }
  .sidebar { position: static; }
}

@media (max-width: 760px) {
  .nav-toggle { display: inline-flex; }
  .main-nav { display: none; position: absolute; top: 68px; left: 16px; right: 16px; flex-direction: column; align-items: stretch; padding: 12px; border: 1px solid var(--line); border-radius: 14px; background: white; box-shadow: var(--shadow); }
  .main-nav.open { display: flex; }
  .hero { padding-top: 52px; }
  .feature-grid, .topic-grid { grid-template-columns: 1fr; }
  .feature-card { min-height: auto; }
  .feature-number { margin-bottom: 20px; }
  .cta-card, .lesson-actions, .footer-grid { display: grid; grid-template-columns: 1fr; }
  .button { width: 100%; }
  .hero-actions .button { width: auto; }
}

@media (max-width: 480px) {
  .container { width: min(calc(100% - 22px), var(--container)); }
  h1 { font-size: 2.42rem; }
  .section { padding: 64px 0; }
  .hero-panel, .feature-card, .module-card, .question-card { padding: 20px; }
  .hero-actions .button { width: 100%; }
  .brand small { display: none; }
}