:root {
  --bg: #f3f5f8;
  --bg-2: #ffffff;
  --panel: #ffffff;
  --panel-strong: #ffffff;
  --line: #e5e7eb;
  --text: #111827;
  --muted: #6b7280;
  --primary: #2563eb;
  --primary-2: #1d4ed8;
  --success: #48d39a;
  --warning: #ffd166;
  --danger: #ff6b6b;
  --shadow: 0 10px 25px rgba(17, 24, 39, 0.08);
  --radius-xl: 16px;
  --radius-lg: 14px;
  --radius-md: 12px;
  --radius-sm: 10px;
  --max: 1180px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Inter", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 18% 10%, rgba(37, 99, 235, 0.16), transparent 46%),
    radial-gradient(circle at 84% 16%, rgba(29, 78, 216, 0.14), transparent 48%),
    radial-gradient(circle at 50% 110%, rgba(16, 185, 129, 0.08), transparent 42%),
    repeating-linear-gradient(0deg, rgba(17, 24, 39, 0.05) 0 1px, transparent 1px 34px),
    repeating-linear-gradient(90deg, rgba(17, 24, 39, 0.05) 0 1px, transparent 1px 34px),
    linear-gradient(180deg, #fafbff 0%, #eef2f7 100%);
  background-size: auto, auto, auto, auto, auto;
  background-position: center, center, center, center, center;
  background-attachment: fixed;
}

a {
  color: inherit;
  text-decoration: none;
}

.page-shell {
  width: min(var(--max), calc(100% - 32px));
  margin: 0 auto;
  padding: 22px 0 44px;
}

body[data-page="home"] .page-shell {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

body[data-page="home"] main {
  flex: 1;
}

.site-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  padding: 18px 0 10px;
}

.site-footer {
  margin-top: auto;
  padding: 14px 0 0;
  border-top: 1px solid rgba(17, 24, 39, 0.08);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  color: var(--muted);
}

.site-footer__note {
  font-size: 0.92rem;
}

.site-footer__cta {
  padding: 8px 12px;
  border-radius: 12px;
  border: 1px solid rgba(17, 24, 39, 0.1);
  background: rgba(255, 255, 255, 0.92);
  color: var(--text);
  font-weight: 800;
  font-size: 0.92rem;
  transition: 0.18s ease;
}

.site-footer__cta:hover {
  transform: translateY(-1px);
  border-color: rgba(37, 99, 235, 0.22);
}

.topbar {
  position: sticky;
  top: 16px;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding: 14px 18px;
  border: 1px solid var(--line);
  border-radius: calc(var(--radius-xl) + 4px);
  background: rgba(255, 255, 255, 0.94);
  backdrop-filter: blur(8px);
  box-shadow: var(--shadow);
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
}

.brand__mark {
  display: grid;
  place-items: center;
  width: 46px;
  height: 46px;
  border-radius: 12px;
  background: linear-gradient(135deg, var(--primary), var(--primary-2));
  color: white;
  font-weight: 800;
  letter-spacing: 0.02em;
  box-shadow: 0 10px 18px rgba(37, 99, 235, 0.22);
}

.brand__text {
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.brand__text strong {
  font-size: 0.98rem;
  line-height: 1.15;
}

.brand__text small {
  color: var(--muted);
  font-size: 0.78rem;
}

.nav {
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav__link {
  padding: 11px 14px;
  border-radius: 999px;
  color: var(--muted);
  font-weight: 600;
  transition: 0.2s ease;
}

.nav__link:hover,
.nav__link.active {
  color: var(--text);
  background: rgba(15, 23, 42, 0.06);
}

.menu-toggle {
  display: none;
  width: 46px;
  height: 46px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: rgba(15, 23, 42, 0.04);
}

.menu-toggle span {
  display: block;
  width: 18px;
  height: 2px;
  margin: 4px auto;
  border-radius: 999px;
  background: var(--text);
}

.hero {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 26px;
  align-items: stretch;
  margin-top: 28px;
}

body[data-page="home"] .hero {
  grid-template-columns: 1fr;
}

body[data-page="home"] .page-shell {
  padding: 18px 0 20px;
}

body[data-page="home"] .hero {
  margin-top: 16px;
}

body[data-page="home"] .hero__content {
  padding: 22px;
}

body[data-page="home"] .content-grid {
  margin-top: 14px;
  gap: 12px;
}

body[data-page="home"] .content-card {
  padding: 18px;
}

.hero__content,
.hero__panel,
.content-card,
.quiz-card,
.info-strip {
  border: 1px solid var(--line);
  background: var(--panel);
  box-shadow: var(--shadow);
}

.hero__content,
.hero__panel {
  border-radius: var(--radius-xl);
  padding: 28px;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  padding: 7px 12px;
  border-radius: 999px;
  background: rgba(37, 99, 235, 0.1);
  color: rgba(37, 99, 235, 0.95);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.hero h1,
.page-hero h1 {
  margin: 16px 0 14px;
  font-size: clamp(2rem, 4vw, 4rem);
  line-height: 1.04;
  letter-spacing: -0.04em;
}

.hero p,
.page-hero p {
  margin: 0;
  color: var(--muted);
  font-size: 1.02rem;
  line-height: 1.7;
}

.hero__actions,
.lesson-footer,
.quiz-controls {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 24px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 46px;
  padding: 0 18px;
  border-radius: 14px;
  border: 1px solid transparent;
  font-weight: 700;
  transition: transform 0.18s ease, background 0.18s ease, border-color 0.18s ease;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn--primary {
  color: #ffffff;
  background: linear-gradient(135deg, var(--primary), #60a5fa);
}

.btn--ghost {
  color: var(--text);
  border-color: rgba(17, 24, 39, 0.12);
  background: rgba(255, 255, 255, 0.9);
}

.hero__stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  margin-top: 22px;
}

.stat-card,
.panel-card,
.topic-card,
.content-card,
.quiz-card,
.info-strip {
  border-radius: var(--radius-lg);
}

.stat-card {
  padding: 16px;
  background: rgba(249, 250, 251, 0.9);
  border: 1px solid rgba(17, 24, 39, 0.06);
}

.stat-card strong,
.page-hero__badge strong,
.info-strip strong {
  display: block;
  font-size: 1.05rem;
}

.stat-card span,
.page-hero__badge small,
.info-strip span {
  color: var(--muted);
  font-size: 0.9rem;
  line-height: 1.55;
}

.hero__panel {
  display: grid;
  gap: 16px;
  align-content: start;
}

.panel-card {
  padding: 22px;
  background: rgba(255, 255, 255, 0.98);
  border: 1px solid rgba(17, 24, 39, 0.06);
}

.panel-card--glow {
  background: rgba(255, 255, 255, 0.98);
}

.panel-card h2,
.panel-card h3,
.section-head h2,
.content-card h2,
.quiz-card h2 {
  margin: 10px 0 10px;
  line-height: 1.18;
  letter-spacing: -0.03em;
}

.panel-card p,
.content-card p,
.content-card li,
.quiz-card p {
  color: var(--muted);
  line-height: 1.7;
}

.chip {
  display: inline-flex;
  align-items: center;
  padding: 7px 11px;
  border-radius: 999px;
  font-size: 0.76rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  background: rgba(37, 99, 235, 0.1);
  color: rgba(37, 99, 235, 0.95);
}

.check-list {
  margin: 0;
  padding-left: 18px;
  color: var(--muted);
  line-height: 1.8;
}

.grid-section {
  margin-top: 28px;
}

.section-head {
  display: flex;
  justify-content: space-between;
  gap: 18px;
  align-items: end;
  margin: 0 0 18px;
}

.section-head p {
  max-width: 520px;
  color: var(--muted);
  line-height: 1.7;
}

.section-kicker {
  display: inline-block;
  margin-bottom: 8px;
  color: rgba(37, 99, 235, 0.92);
  font-size: 0.78rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.topic-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
}

.topic-card {
  display: flex;
  flex-direction: column;
  min-height: 220px;
  padding: 22px;
  background: rgba(255, 255, 255, 0.98);
  border: 1px solid rgba(17, 24, 39, 0.06);
  transition: transform 0.18s ease, border-color 0.18s ease, background 0.18s ease;
}

.topic-card:hover {
  transform: translateY(-4px);
  border-color: rgba(37, 99, 235, 0.22);
}

.topic-icon {
  font-size: 1.8rem;
  line-height: 1;
}

.topic-card h3 {
  margin: 16px 0 10px;
  font-size: 1.2rem;
}

.topic-card p {
  margin: 0;
  color: var(--muted);
  line-height: 1.65;
}

.topic-link {
  margin-top: auto;
  color: rgba(37, 99, 235, 0.92);
  font-weight: 700;
}

.pill-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 14px;
}

.pill-link {
  display: inline-flex;
  align-items: center;
  min-height: 40px;
  padding: 0 14px;
  border-radius: 999px;
  border: 1px solid rgba(17, 24, 39, 0.1);
  background: rgba(255, 255, 255, 0.98);
  font-weight: 700;
  transition: 0.18s ease;
}

.pill-link:hover {
  transform: translateY(-1px);
  border-color: rgba(37, 99, 235, 0.22);
}

.info-strip {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
  margin-top: 24px;
  padding: 20px 22px;
}

.info-strip__item {
  padding: 12px 6px;
}

.content-page {
  margin-top: 26px;
}

.page-hero {
  display: grid;
  grid-template-columns: 8.6fr 0.55fr;
  gap: 18px;
  align-items: stretch;
  padding: 28px;
  border: 1px solid var(--line);
  border-radius: var(--radius-xl);
  background: rgba(255, 255, 255, 0.98);
  box-shadow: var(--shadow);
}

.page-hero--light {
  border-color: rgba(15, 23, 42, 0.08);
}

.page-hero__badge {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 8px;
  padding: 22px;
  border-radius: 22px;
  background: rgba(249, 250, 251, 0.9);
  border: 1px solid rgba(17, 24, 39, 0.06);
}

.content-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  margin-top: 18px;
}

.content-grid--3 {
  grid-template-columns: repeat(3, 1fr);
}

.content-card {
  padding: 22px;
  background: rgba(255, 255, 255, 0.98);
}

.content-card--compact {
  padding: 18px;
}

.content-card--accent {
  background: rgba(249, 250, 251, 0.92);
}

.content-card--wide {
  grid-column: 1 / -1;
}

.lesson-footer {
  margin-top: 20px;
}

.quiz-card {
  padding: 24px;
  background: rgba(255, 255, 255, 0.86);
}

.quiz-meta {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: center;
  margin-bottom: 12px;
}

.quiz-progress {
  color: var(--muted);
  font-size: 0.92rem;
}

.home-question-title {
  margin: 10px 0 0;
  font-size: 1.25rem;
  letter-spacing: -0.02em;
}

.answers {
  display: grid;
  gap: 12px;
  margin-top: 18px;
}

.answer-btn {
  min-height: 54px;
  padding: 12px 14px;
  border-radius: 16px;
  border: 1px solid rgba(15, 23, 42, 0.1);
  background: rgba(255, 255, 255, 0.72);
  color: var(--text);
  text-align: left;
  font: inherit;
  font-weight: 600;
  cursor: pointer;
  transition: 0.18s ease;
}

.answer-btn:hover {
  transform: translateY(-1px);
  border-color: rgba(37, 99, 235, 0.22);
}

.answer-btn.correct {
  border-color: rgba(72, 211, 154, 0.55);
  background: rgba(72, 211, 154, 0.12);
}

.answer-btn.wrong {
  border-color: rgba(255, 107, 107, 0.6);
  background: rgba(255, 107, 107, 0.1);
}

.quiz-result {
  margin-top: 18px;
  padding: 18px;
  border-radius: 18px;
  background: rgba(37, 99, 235, 0.06);
  border: 1px solid rgba(37, 99, 235, 0.14);
}

.quiz-result.is-correct {
  border-color: rgba(72, 211, 154, 0.4);
  background: rgba(72, 211, 154, 0.1);
}

.quiz-result.is-wrong {
  border-color: rgba(255, 107, 107, 0.45);
  background: rgba(255, 107, 107, 0.1);
}

.quiz-result h3 {
  margin: 0 0 8px;
}

.card-title {
  margin: 0 0 10px;
  font-size: 1.02rem;
  letter-spacing: -0.02em;
}

.card-lead {
  margin: 0;
  color: var(--muted);
  line-height: 1.7;
}

.ulearn-layout {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 16px;
  margin-top: 18px;
  align-items: start;
}

.ulearn-nav {
  border: 1px solid var(--line);
  border-radius: var(--radius-xl);
  background: rgba(255, 255, 255, 0.98);
  box-shadow: var(--shadow);
  padding: 16px;
  position: sticky;
  top: 18px;
}

.ulearn-brand {
  padding: 6px 4px 14px;
}

.ulearn-links {
  display: grid;
  gap: 8px;
}

.ulearn-link {
  display: grid;
  gap: 6px;
  padding: 12px 12px;
  border-radius: 12px;
  border: 1px solid rgba(17, 24, 39, 0.06);
  background: rgba(249, 250, 251, 0.92);
  transition: 0.18s ease;
}

.ulearn-link:hover {
  border-color: rgba(37, 99, 235, 0.18);
  transform: translateY(-1px);
}

.ulearn-link.active {
  background: rgba(37, 99, 235, 0.08);
  border-color: rgba(37, 99, 235, 0.22);
}

.ulearn-link__title {
  font-weight: 800;
  letter-spacing: -0.02em;
}

.ulearn-link__meta {
  color: var(--muted);
  line-height: 1.55;
  font-size: 0.92rem;
}

.ulearn-main {
  border: 1px solid var(--line);
  border-radius: var(--radius-xl);
  background: rgba(255, 255, 255, 0.98);
  box-shadow: var(--shadow);
  padding: 18px;
}

.ulearn-lesson-head h2 {
  margin: 0 0 8px;
  letter-spacing: -0.03em;
}

.ulearn-lesson-head p {
  margin: 0;
  color: var(--muted);
  line-height: 1.65;
}

@media (max-width: 1024px) {

  .hero,
  .page-hero,
  .section-head {
    grid-template-columns: 1fr;
  }

  .topic-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .hero__stats,
  .info-strip,
  .content-grid {
    grid-template-columns: 1fr;
  }

  .content-grid--3 {
    grid-template-columns: 1fr;
  }

  .ulearn-layout {
    grid-template-columns: 1fr;
  }

  .ulearn-nav {
    position: static;
  }
}

@media (max-width: 760px) {
  .topbar {
    flex-wrap: wrap;
    top: 10px;
  }

  .menu-toggle {
    display: inline-grid;
    place-items: center;
    margin-left: auto;
  }

  .nav {
    display: none;
    width: 100%;
    flex-direction: column;
    align-items: stretch;
    padding-top: 10px;
  }

  .nav.nav--open {
    display: flex;
  }

  .nav__link {
    width: 100%;
    border-radius: 16px;
  }

  .page-shell {
    width: min(var(--max), calc(100% - 20px));
    padding-top: 10px;
  }

  .topic-grid {
    grid-template-columns: 1fr;
  }

  .hero__content,
  .hero__panel,
  .content-card,
  .quiz-card,
  .page-hero {
    padding: 20px;
  }

  .quiz-progressbar {
    width: 100%;
    height: 10px;
    border-radius: 999px;
    overflow: hidden;
    margin: 12px 0 20px;
    background: rgba(255, 255, 255, .08);
  }

  .quiz-progressbar__fill {
    height: 100%;
    width: 0;
    transition: width .25s ease;
    background: linear-gradient(90deg, #22c55e, #4ade80);
  }
}