:root {
  --bg: #0f172a;
  --bg-soft: #1e293b;
  --card: #1e293b;
  --border: #334155;
  --text: #e2e8f0;
  --muted: #94a3b8;
  --accent: #38bdf8;
  --accent-2: #818cf8;
  --green: #34d399;
  --yellow: #fbbf24;
  --red: #f87171;
  --radius: 12px;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.35);
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
}

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

img {
  max-width: 100%;
}

.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 20px;
}

/* ===== Header ===== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(15, 23, 42, 0.9);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 20px;
  color: var(--text);
}

.brand .logo {
  display: grid;
  place-items: center;
  width: 36px;
  height: 36px;
  border-radius: 10px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  color: #0f172a;
  font-weight: 800;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 22px;
  list-style: none;
}

.nav-links a {
  color: var(--muted);
  font-weight: 500;
  transition: color 0.2s;
}

.nav-links a:hover {
  color: var(--text);
}

.nav-links .nav-btn {
  padding: 8px 16px;
  border-radius: 8px;
  background: var(--accent);
  color: #0f172a;
  font-weight: 600;
  transition: transform 0.2s, opacity 0.2s;
}

.nav-links .nav-btn:hover {
  color: #0f172a;
  transform: translateY(-1px);
  opacity: 0.9;
}

/* ===== Hero ===== */
.hero {
  padding: 90px 0 70px;
  text-align: center;
  background: radial-gradient(600px 300px at 50% 0%, rgba(56, 189, 248, 0.15), transparent 70%);
}

.hero .badge {
  display: inline-block;
  padding: 6px 14px;
  border-radius: 999px;
  background: rgba(56, 189, 248, 0.12);
  border: 1px solid rgba(56, 189, 248, 0.35);
  color: var(--accent);
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 20px;
}

.hero h1 {
  font-size: clamp(34px, 6vw, 58px);
  line-height: 1.15;
  margin-bottom: 18px;
}

.hero h1 .grad {
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero p {
  max-width: 640px;
  margin: 0 auto 30px;
  color: var(--muted);
  font-size: 18px;
}

.hero-actions {
  display: flex;
  gap: 14px;
  justify-content: center;
  flex-wrap: wrap;
}

.continue-bar {
  max-width: 620px;
  margin: 0 auto 26px;
  padding: 12px 18px;
  border: 1px solid rgba(56, 189, 248, 0.35);
  background: rgba(56, 189, 248, 0.08);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  flex-wrap: wrap;
  text-align: left;
}

.continue-bar.hidden {
  display: none;
}

.continue-bar .cbt-tag {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--accent);
  font-weight: 700;
  margin-bottom: 2px;
}

.continue-bar .cbt-title {
  font-size: 15px;
  color: var(--text);
}

.btn {
  display: inline-block;
  padding: 12px 24px;
  border-radius: 10px;
  font-weight: 600;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform 0.2s, opacity 0.2s;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  color: #0f172a;
}

.btn-primary:hover {
  transform: translateY(-2px);
  opacity: 0.95;
}

.btn-outline {
  border-color: var(--border);
  color: var(--text);
  background: transparent;
}

.btn-outline:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 40px;
  margin-top: 50px;
  flex-wrap: wrap;
}

.stat b {
  display: block;
  font-size: 28px;
  color: var(--text);
}

.stat span {
  color: var(--muted);
  font-size: 14px;
}

/* ===== Sections ===== */
.section {
  padding: 70px 0;
}

.section-head {
  text-align: center;
  max-width: 620px;
  margin: 0 auto 40px;
}

.section-head h2 {
  font-size: 30px;
  margin-bottom: 10px;
}

.section-head p {
  color: var(--muted);
}

/* ===== Course cards on home ===== */
.filter-bar {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  justify-content: center;
  margin: 0 auto 28px;
  max-width: 620px;
}

.filter-bar input,
.filter-bar select {
  padding: 10px 14px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--text);
  font-size: 14px;
  font-family: inherit;
  outline: none;
  transition: border-color 0.2s;
}

.filter-bar input {
  flex: 1;
  min-width: 200px;
}

.filter-bar input::placeholder {
  color: var(--muted);
}

.filter-bar input:focus,
.filter-bar select:focus {
  border-color: var(--accent);
}

.cat-chips {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: center;
  flex-basis: 100%;
}

.chip {
  padding: 6px 14px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--muted);
  font-size: 13px;
  font-family: inherit;
  cursor: pointer;
  transition: border-color 0.15s, color 0.15s, background 0.15s;
}

.chip:hover {
  border-color: var(--accent);
  color: var(--text);
}

.chip.active {
  border-color: var(--accent);
  background: rgba(56, 189, 248, 0.14);
  color: var(--accent);
  font-weight: 600;
}

.lesson-card.hidden-card {
  display: none;
}

.filter-empty {
  grid-column: 1 / -1;
  text-align: center;
  color: var(--muted);
  padding: 28px 0;
}

.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 24px;
}

.course-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  transition: transform 0.25s, border-color 0.25s, box-shadow 0.25s;
}

.course-card:hover {
  transform: translateY(-4px);
  border-color: var(--accent);
  box-shadow: var(--shadow);
}

.course-card .icon {
  display: grid;
  place-items: center;
  width: 52px;
  height: 52px;
  border-radius: 14px;
  font-size: 24px;
  margin-bottom: 18px;
}

.icon-html { background: rgba(249, 115, 22, 0.15); }
.icon-css { background: rgba(56, 189, 248, 0.15); }
.icon-js { background: rgba(250, 204, 21, 0.15); }

.course-card h3 {
  font-size: 20px;
  margin-bottom: 10px;
}

.course-card p {
  color: var(--muted);
  font-size: 15px;
  margin-bottom: 20px;
}

.course-card .meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 14px;
  color: var(--muted);
}

.shimmer {
  color: var(--muted);
  background: var(--muted);
}

.count {
  color: var(--muted);
  font-size: 14px;
}

/* progress bar */
.progress {
  height: 8px;
  border-radius: 99px;
  background: var(--border);
  overflow: hidden;
  margin-top: 16px;
}

.progress-inner {
  height: 100%;
  border-radius: 99px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  width: 0%;
  transition: width 0.4s;
}

/* ===== Lesson cards ===== */
.lesson-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
}

.lesson-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px;
  display: flex;
  flex-direction: column;
  transition: transform 0.2s, border-color 0.2s;
}

.lesson-card:hover {
  transform: translateY(-3px);
  border-color: var(--accent);
}

.lesson-card .num {
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  margin-bottom: 12px;
}

.num-html { color: #fb923c; }
.num-css { color: var(--accent); }
.num-js { color: #facc15; }
.num-git { color: #f472b6; }
.num-web { color: #a3e635; }
.num-tools { color: #a78bfa; }
.num-react { color: #2dd4bf; }
.num-project { color: #818cf8; }
.num-node { color: #f97316; }
.num-data { color: #22c55e; }
.num-sec { color: #ef4444; }
.num-ts { color: #2563eb; }
.num-pwa { color: #0ea5e9; }
.num-perf { color: #10b981; }
.num-media { color: #e879f9; }
.num-devops { color: #64748b; }
.num-career { color: #fbbf24; }
.num-fullstack { color: #14b8a6; }
.num-websocket { color: #06b6d4; }
.num-redis { color: #b91c1c; }
.num-api { color: #3b82f6; }
.num-next { color: #a855f7; }
.num-a11y { color: #f59e0b; }
.num-three { color: #7c3aed; }
.num-lint { color: #f43f5e; }
.num-patterns { color: #0891b2; }
.num-teamwork { color: #d97706; }
.num-vps { color: #475569; }
.num-cloud { color: #38bdf8; }
.num-monitoring { color: #16a34a; }
.num-algo { color: #9333ea; }
.num-capstone { color: #0f766e; }
.num-ci { color: #65a30d; }
.num-pg { color: #0369a1; }
.num-graphql { color: #c026d3; }
.num-search { color: #ca8a04; }
.num-storybook { color: #ec4899; }
.num-tdd { color: #4d7c0f; }
.num-owasp { color: #991b1b; }
.num-audit { color: #115e59; }
.num-k8s { color: #4338ca; }
.num-cdn { color: #7e22ce; }
.num-iac { color: #334155; }
.num-figma { color: #be185d; }
.num-ux { color: #15803d; }
.num-oss { color: #60a5fa; }
.num-freelance { color: #92400e; }
.num-lang { color: #5b21b6; }
.num-dash { color: #059669; }
.num-shop { color: #c2410c; }
.num-webcomp { color: #0d9488; }
.num-i18n { color: #b45309; }
.num-dnd { color: #65a30d; }
.num-sys { color: #475569; }
.num-arch { color: #7c3aed; }
.num-orm { color: #16a34a; }
.num-queue { color: #ea580c; }
.num-rl { color: #dc2626; }
.num-idem { color: #2563eb; }
.num-agile { color: #db2777; }
.num-docs { color: #0891b2; }
.num-hrint { color: #a21caf; }
.num-rn { color: #0ea5e9; }
.num-desktop { color: #6366f1; }
.num-regex { color: #be123c; }
.num-dates { color: #6d28d9; }
.num-subs { color: #10b981; }
.num-kanban { color: #64748b; }

.lesson-card h3 {
  font-size: 17px;
  margin-bottom: 8px;
  color: var(--text);
}

.lesson-card p {
  color: var(--muted);
  font-size: 14px;
  flex-grow: 1;
}

.lesson-card .go {
  margin-top: 16px;
  font-size: 14px;
  color: var(--accent);
}

.done {
  border-color: rgba(52, 211, 153, 0.4) !important;
}

.done .check {
  color: var(--green);
  font-size: 13px;
  margin-top: 8px;
  font-weight: 600;
}

/* ===== Features ===== */
.features {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 20px;
}

.feature {
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
}

.feature .f-icon {
  font-size: 26px;
  margin-bottom: 12px;
}

.feature h4 {
  margin-bottom: 8px;
}

.feature p {
  color: var(--muted);
  font-size: 14px;
}

/* ===== Lesson page layout ===== */
.lesson-layout {
  display: grid;
  grid-template-columns: 260px 1fr;
  gap: 32px;
  align-items: start;
  padding: 36px 0 60px;
}

.sidebar {
  position: sticky;
  top: 84px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
}

.sidebar h4 {
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--muted);
  margin-bottom: 12px;
}

.sidebar-toc {
  margin-bottom: 16px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--border);
}

.sidebar-toc h4 {
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--muted);
  margin-bottom: 10px;
}

.sidebar .sidebar-toc ul {
  list-style: none;
  margin: 0;
  padding: 0;
  max-height: none;
  overflow: visible;
}

.sidebar .sidebar-toc a {
  display: block;
  padding: 6px 12px;
  font-size: 13px;
  color: var(--muted);
  border-radius: 8px;
  transition: background 0.2s, color 0.2s;
}

.sidebar .sidebar-toc a:hover {
  background: rgba(56, 189, 248, 0.1);
  color: var(--text);
}

.sidebar .sidebar-toc a.active {
  background: rgba(56, 189, 248, 0.14);
  color: var(--accent);
  font-weight: 600;
}

/* читательский прогресс */
.read-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  width: 0;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  z-index: 100;
  pointer-events: none;
}

.lesson-meta {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 24px;
}

.reading-time {
  font-size: 13px;
  color: var(--muted);
  background: var(--bg-soft);
  border: 1px solid var(--border);
  padding: 4px 12px;
  border-radius: 999px;
}

.sidebar ul {
  list-style: none;
  max-height: calc(100vh - 160px);
  overflow-y: auto;
  padding-right: 4px;
}

.sidebar li {
  border-radius: 8px;
  margin-bottom: 6px;
}

.sidebar li.sb-cat {
  margin-top: 16px;
  margin-bottom: 6px;
  padding: 0 12px;
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: var(--muted);
}

.sidebar a {
  display: block;
  padding: 8px 12px;
  font-size: 14px;
  color: var(--muted);
  border-radius: 8px;
  transition: background 0.2s, color 0.2s;
}

.sidebar a:hover {
  background: rgba(56, 189, 248, 0.1);
  color: var(--text);
}

.sidebar a.active {
  background: rgba(56, 189, 248, 0.15);
  color: var(--accent);
  font-weight: 600;
}

/* мобильное оглавление */
.mobile-toc {
  display: none;
  margin-bottom: 24px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg-soft);
}

.mobile-toc summary {
  cursor: pointer;
  padding: 13px 16px;
  font-weight: 600;
  font-size: 15px;
  color: var(--text);
}

.mobile-toc ul {
  list-style: none;
  margin: 0;
  padding: 0 16px 14px;
}

.mobile-toc a {
  display: block;
  padding: 7px 0;
  font-size: 14px;
  color: var(--muted);
  border-top: 1px solid var(--border);
}

.mobile-toc a:hover {
  color: var(--accent);
}

.lesson-body {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 36px;
  min-width: 0;
}

.lesson-body .num {
  font-size: 14px;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--accent);
  font-weight: 700;
  display: block;
  margin-bottom: 8px;
}

.lesson-body h1 {
  font-size: 30px;
  margin-bottom: 8px;
}

.lesson-body .lead {
  color: var(--muted);
  margin-bottom: 28px;
}

.lesson-body h2 {
  font-size: 22px;
  margin: 34px 0 14px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border);
}

.lesson-body h3 {
  font-size: 17px;
  margin: 22px 0 10px;
}

.lesson-body p {
  margin-bottom: 14px;
}

.lesson-body ul,
.lesson-body ol {
  margin: 0 0 16px 22px;
}

.lesson-body li {
  margin-bottom: 6px;
}

.lesson-body strong {
  color: #fff;
}

/* code */
pre {
  background: #0b1220;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 16px 18px;
  overflow-x: auto;
  margin: 14px 0 20px;
}

code {
  font-family: "Cascadia Code", Consolas, "Courier New", monospace;
  font-size: 13.5px;
  color: #f8fafc;
}

:not(pre) > code {
  background: rgba(56, 189, 248, 0.12);
  color: #7dd3fc;
  padding: 2px 6px;
  border-radius: 5px;
  font-size: 13px;
}

.token.tag { color: #38bdf8; }
.token.attr { color: #fbbf24; }
.token.str  { color: #34d399; }
.token.cmt  { color: #64748b; font-style: italic; }
.token.num  { color: #f472b6; }
.token.key  { color: #c084fc; }
.token.fn   { color: #fbbf24; }

/* callout */
.callout {
  display: flex;
  gap: 12px;
  padding: 14px 18px;
  border-radius: 10px;
  margin: 18px 0;
  font-size: 15px;
}

.callout .e {
  font-size: 20px;
}

.callout.tip { background: rgba(52, 211, 153, 0.1); border-left: 4px solid var(--green); }
.callout.info { background: rgba(56, 189, 248, 0.1); border-left: 4px solid var(--accent); }
.callout.warn { background: rgba(251, 191, 36, 0.1); border-left: 4px solid var(--yellow); }

/* table */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 14px 0 22px;
  font-size: 14px;
}

th, td {
  text-align: left;
  padding: 10px 12px;
  border-bottom: 1px solid var(--border);
}

th {
  color: var(--muted);
  font-weight: 600;
}

tr:hover td {
  background: rgba(56, 189, 248, 0.04);
}

/* practice / result boxes */
.result {
  background: #0b1220;
  border: 1px dashed var(--border);
  border-radius: 10px;
  padding: 20px;
  margin: 14px 0 20px;
}

.result .demo-row {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  align-items: center;
}

.demo-box {
  width: 64px;
  height: 64px;
  border-radius: 8px;
  background: var(--accent);
  color: #0f172a;
  display: grid;
  place-items: center;
  font-weight: 700;
}

.demo-box.green { background: var(--green); }
.demo-box.yellow { background: var(--yellow); }
.demo-box.red { background: var(--red); }
.demo-box.purple { background: var(--accent-2); }

.demo-strip {
  display: inline-flex;
  gap: 28px;
  border: 2px solid var(--green);
  padding: 18px 26px;
  border-radius: 12px;
}

.demo-pill {
  background: var(--green);
  color: #0f172a;
  padding: 6px 14px;
  border-radius: 999px;
  font-weight: 700;
}

/* progress + toggle */
#lessonProgress {
  display: inline-block;
  margin: 3px 0;
}

/* interactive demo */
.interactive {
  margin-top: 14px;
}

.interactive button,
.practice-control input {
  padding: 8px 14px;
  margin: 6px 6px 0 0;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--bg-soft);
  color: var(--text);
  font-size: 14px;
  cursor: pointer;
}

.interactive button:hover {
  border-color: var(--accent);
  color: var(--accent);
}

#clickFeedback {
  margin-top: 12px;
  min-height: 24px;
  font-size: 15px;
}

/* lesson nav buttons */
.lesson-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 40px;
}

.next-lesson {
  margin: 22px 0 0;
  text-align: center;
}

.next-lesson p {
  color: var(--green);
  font-weight: 600;
  margin: 0;
}

.lesson-nav .btn {
  border-color: var(--border);
  background: var(--bg-soft);
  color: var(--text);
}

.lesson-nav .btn:hover {
  border-color: var(--accent);
  color: var(--accent);
}

/* ===== Footer ===== */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 34px 0;
  text-align: center;
  color: var(--muted);
  font-size: 14px;
  margin-top: 40px;
}

.site-footer a {
  color: var(--muted);
  border-bottom: 1px dashed var(--border);
}

/* ===== Responsive ===== */
@media (max-width: 860px) {
  .lesson-layout {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    display: none;
  }

  .mobile-toc {
    display: block;
  }
}

@media (max-width: 640px) {
  .nav-links li:not(.nav-cta) {
    display: none;
  }

  .hero {
    padding: 60px 0 50px;
  }

  .lesson-body {
    padding: 24px 18px;
  }
}

/* ===== Sparkline/scrollbar ===== */
::-webkit-scrollbar {
  width: 10px;
  height: 10px;
}

::-webkit-scrollbar-track {
  background: var(--bg);
}

::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 99px;
}

::-webkit-scrollbar-thumb:hover {
  background: #475569;
}

/* ===== Light theme ===== */
html.light {
  --bg: #f6f8fb;
  --bg-soft: #eef2f7;
  --card: #ffffff;
  --border: #d7dfe9;
  --text: #0f172a;
  --muted: #5b6b7f;
  --shadow: 0 12px 34px rgba(15, 23, 42, 0.08);
}

html.light .site-header {
  background: rgba(255, 255, 255, 0.85);
  border-bottom-color: rgba(15, 23, 42, 0.08);
}

html.light .hero {
  background: radial-gradient(600px 300px at 50% 0%, rgba(56, 189, 248, 0.22), transparent 70%);
  border-bottom-color: rgba(15, 23, 42, 0.08);
}

html.light .nav-links a {
  color: var(--text);
}

html.light .nav-links a:hover {
  color: var(--accent);
}

html.light .brand {
  color: var(--text);
}

html.light .nav-btn,
html.light .btn {
  color: var(--text);
}

html.light .nav-btn:hover {
  color: var(--accent);
}

html.light .lesson-body strong,
html.light p strong {
  color: var(--text);
}

html.light p {
  color: var(--text);
}

html.light .hero p,
html.light .hero-sub,
html.light p.lead {
  color: var(--muted);
}

html.light .lesson-card h3,
html.light .feature h4,
html.light h1,
html.light h2,
html.light h3,
html.light h4 {
  color: var(--text);
}

html.light :not(pre) > code {
  background: rgba(56, 189, 248, 0.14);
  color: #0562a1;
}

html.light .result {
  background: #0b1220;
  color: #e2e8f0;
}

html.light .callout {
  border-color: var(--border);
}

html.light .sidebar .active {
  color: var(--accent);
}

html.light .menu-open .nav-links {
  background: #ffffff;
}

/* ===== Кнопка меню (бургер) ===== */
.burger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 42px;
  height: 42px;
  padding: 10px;
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  z-index: 60;
}

.burger span {
  display: block;
  height: 2px;
  border-radius: 2px;
  background: var(--text);
  transition: transform 0.25s ease, opacity 0.25s ease;
}

body.menu-open .burger span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

body.menu-open .burger span:nth-child(2) {
  opacity: 0;
}

body.menu-open .burger span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* ===== Кнопка темы ===== */
.theme-toggle {
  width: 42px;
  height: 42px;
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--border);
  background: var(--bg-soft);
  color: var(--text);
  border-radius: 8px;
  font-size: 18px;
  line-height: 1;
  cursor: pointer;
  transition: border-color 0.2s, transform 0.2s;
}

.theme-toggle:hover {
  border-color: var(--accent);
  transform: scale(1.06);
}

html.light .theme-toggle {
  background: var(--bg-soft);
}

/* ===== Кнопка копирования ===== */
pre {
  position: relative;
}

.copy-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  padding: 4px 10px;
  font-family: inherit;
  font-size: 12px;
  color: var(--muted);
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border);
  border-radius: 6px;
  cursor: pointer;
  opacity: 1;
  transition: color 0.2s, border-color 0.2s, background 0.2s;
  z-index: 2;
}

.copy-btn:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: rgba(56, 189, 248, 0.12);
}

/* ===== Квиз ===== */
.quiz {
  margin: 34px 0 10px;
  padding: 22px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-soft);
}

.quiz h2 {
  margin: 0 0 8px;
  padding: 0;
  border: none;
}

.quiz > p {
  color: var(--muted);
  font-size: 15px;
  margin-bottom: 14px;
}

.quiz-form {
  margin-top: 18px;
}

.q {
  margin-bottom: 20px;
}

.q-title {
  font-weight: 600;
  margin-bottom: 8px;
}

.q-opt {
  display: block;
  width: 100%;
  text-align: left;
  margin: 6px 0;
  padding: 10px 14px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-size: 15px;
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s;
}

.q-opt:hover {
  border-color: var(--accent);
}

.q-opt.picked {
  border-color: var(--accent);
  background: rgba(56, 189, 248, 0.12);
}

.q-opt.ok {
  border-color: var(--green);
  background: rgba(52, 211, 153, 0.14);
  color: var(--green);
}

.q-opt.no {
  border-color: var(--red);
  background: rgba(248, 113, 113, 0.1);
  color: var(--red);
}

.q.wrong .q-title {
  color: var(--red);
}

.q.correct .q-title {
  color: var(--green);
}

.q-explain {
  display: none;
  margin-top: 8px;
  padding: 8px 12px;
  border-radius: 8px;
  font-size: 13.5px;
  line-height: 1.5;
}

.q-explain.q-explain-good {
  display: block;
  background: rgba(52, 211, 153, 0.1);
  color: var(--green);
  border-left: 3px solid var(--green);
}

.q-explain.q-explain-bad {
  display: block;
  background: rgba(248, 113, 113, 0.1);
  color: var(--red);
  border-left: 3px solid var(--red);
}

.quiz-actions {
  margin: 10px 0 8px;
}

.quiz-score {
  font-weight: 600;
  margin-top: 10px;
}

.quiz-score.good {
  color: var(--green);
}

/* ===== Песочница ===== */
.sandbox {
  margin: 34px 0 10px;
  padding: 22px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-soft);
}

.sandbox h2 {
  margin: 0 0 8px;
  padding: 0;
  border: none;
}

.sandbox > p {
  color: var(--muted);
  font-size: 15px;
}

.sandbox-field {
  margin-top: 12px;
}

.sandbox-label {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--muted);
  font-weight: 700;
  margin-bottom: 6px;
}

.sandbox-code {
  width: 100%;
  height: 90px;
  font-family: "Cascadia Code", Consolas, "Courier New", monospace;
  font-size: 13px;
  color: #f8fafc;
  background: #0b1220;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px 12px;
  resize: vertical;
  outline: none;
  box-sizing: border-box;
}

.sandbox-code:focus {
  border-color: var(--accent);
}

.sandbox-actions {
  margin: 14px 0 8px;
}

.sandbox-frame {
  width: 100%;
  height: 260px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: #ffffff;
}

/* ===== Кнопка «наверх» ===== */
.back-top {
  position: fixed;
  right: 20px;
  bottom: 20px;
  z-index: 60;
  width: 46px;
  height: 46px;
  font-size: 20px;
  line-height: 1;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--text);
  cursor: pointer;
  box-shadow: var(--shadow);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.25s, transform 0.25s, visibility 0.25s;
}

.back-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-top:hover {
  border-color: var(--accent);
  color: var(--accent);
}

/* ===== Сертификат ===== */
.certificate {
  display: none;
  margin-top: 40px;
  padding: 40px 28px;
  text-align: center;
  border: 1px solid var(--border);
  border-radius: 16px;
  background: linear-gradient(135deg, rgba(56, 189, 248, 0.14), rgba(129, 140, 248, 0.14));
}

.certificate.show {
  display: block;
  animation: certIn 0.5s ease;
}

@keyframes certIn {
  from {
    opacity: 0;
    transform: scale(0.96);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

.cert-emoji {
  font-size: 48px;
  line-height: 1;
}

.certificate h3 {
  font-size: 26px;
  margin: 10px 0 6px;
  color: var(--text);
}

.cert-sub {
  color: var(--muted);
  margin-bottom: 18px;
}

.cert-date,
.cert-stats {
  color: var(--muted);
  font-size: 14px;
  margin: 4px 0;
}

/* ===== Мобильное меню ===== */
@media (max-width: 640px) {
  .burger {
    display: flex;
  }

  .nav-links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    flex-direction: column;
    gap: 0;
    background: var(--bg-soft);
    border-bottom: 1px solid var(--border);
    padding: 8px 0;
  }

  .nav-links li:not(.nav-cta) {
    display: block;
  }

  body.menu-open .nav-links {
    display: flex;
  }

  .nav-links a {
    display: block;
    padding: 12px 20px;
  }
}

.nav-links {
  margin-left: auto;
}

.theme-toggle {
  margin-left: 10px;
}

/* ===== Панели: активность, бейджи, разделы ===== */
.panel-box {
  margin-top: 32px;
  padding: 24px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card);
}

.panel-box h3 {
  font-size: 18px;
  margin-bottom: 14px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}

.panel-box .streak {
  font-size: 14px;
  color: var(--yellow);
  background: rgba(251, 191, 36, 0.12);
  padding: 4px 12px;
  border-radius: 999px;
  font-weight: 700;
}

.act-grid {
  display: grid;
  grid-template-columns: repeat(15, 1fr);
  gap: 5px;
}

.act-cell {
  aspect-ratio: 1;
  border-radius: 5px;
  background: var(--bg-soft);
  border: 1px solid var(--border);
}

.act-cell.on {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border-color: transparent;
}

.ach-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 12px;
}

.ach {
  padding: 16px 12px;
  text-align: center;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--bg-soft);
  opacity: 0.45;
  filter: grayscale(0.7);
  transition: opacity 0.3s, transform 0.3s;
}

.ach.unlocked {
  opacity: 1;
  filter: none;
  border-color: rgba(52, 211, 153, 0.45);
  background: linear-gradient(160deg, rgba(52, 211, 153, 0.12), rgba(56, 189, 248, 0.08));
}

.ach .ach-emoji {
  display: block;
  font-size: 30px;
  line-height: 1;
  margin-bottom: 8px;
}

.ach b {
  display: block;
  font-size: 14px;
  color: var(--text);
  margin-bottom: 4px;
}

.ach small {
  font-size: 12px;
  color: var(--muted);
  line-height: 1.4;
  display: block;
}

.sec-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.sec-top {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  font-size: 14px;
  margin-bottom: 5px;
}

.sec-top b {
  color: var(--text);
}

.sec-top span {
  color: var(--muted);
  white-space: nowrap;
}

.sec-row .progress {
  margin: 0;
}

/* ===== Палитра Ctrl+K ===== */
.palette {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 120;
  background: rgba(15, 23, 42, 0.6);
  padding: 14vh 16px 16px;
}

.palette.show {
  display: block;
}

.palette-box {
  max-width: 520px;
  margin: 0 auto;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 14px;
  overflow: hidden;
  box-shadow: var(--shadow);
}

.palette-box input {
  width: 100%;
  padding: 16px 18px;
  border: none;
  border-bottom: 1px solid var(--border);
  background: transparent;
  color: var(--text);
  font-size: 16px;
  font-family: inherit;
  outline: none;
}

.palette-hint {
  padding: 6px 18px;
  font-size: 12px;
  color: var(--muted);
  border-bottom: 1px solid var(--border);
}

.palette-results {
  max-height: 46vh;
  overflow-y: auto;
}

.palette-item {
  display: block;
  padding: 12px 18px;
  color: var(--text);
  font-size: 15px;
  border-bottom: 1px solid var(--border);
}

.palette-item:hover {
  background: rgba(56, 189, 248, 0.1);
  color: var(--accent);
}

.palette-empty {
  padding: 16px 18px;
  color: var(--muted);
  font-size: 14px;
}

/* ===== Мелкие кнопки в шапке урока ===== */
.meta-btn {
  padding: 5px 12px;
  font-size: 13px;
  border-radius: 999px;
}

/* ===== Фокус ===== */
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

input:focus-visible,
select:focus-visible,
textarea:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
}

/* ===== Печать / PDF ===== */
@media print {
  body {
    background: #ffffff;
    color: #111827;
  }

  .site-header,
  .site-footer,
  .sidebar,
  .burger,
  .theme-toggle,
  .back-top,
  .copy-btn,
  .progress-wrap,
  .toggle-wrap,
  .lesson-nav,
  .next-lesson,
  .mobile-toc,
  .quiz,
  .sandbox,
  .filter-bar,
  .read-progress {
    display: none !important;
  }

  html.light body {
    --bg: #ffffff;
    --text: #111827;
    --muted: #4b5563;
    --border: #d1d5db;
    --card: #ffffff;
  }

  .lesson-layout {
    display: block;
    padding: 0;
  }

  .lesson-body,
  .lesson-body code {
    border: none;
    box-shadow: none;
    padding: 0;
  }

  pre {
    background: #f3f4f6 !important;
    border-color: #d1d5db;
    box-decoration-break: clone;
  }

  a {
    color: #111827;
  }

  .lesson-body strong,
  code {
    color: #111827;
  }

  :not(pre) > code {
    background: #f3f4f6;
    color: #111827;
  }

  .lesson-body h1,
  .lesson-body h2 {
    page-break-after: avoid;
  }

  pre,
  table,
  .result {
    page-break-inside: avoid;
  }

  .certificate {
    border: 2px solid #111827;
    color: #111827;
    background: #ffffff !important;
  }
}

body.print-cert .hero,
body.print-cert #lessons,
body.print-cert #features,
body.print-cert #sectionsPanel,
body.print-cert #achievements,
body.print-cert #activityStats,
body.print-cert #globalStats,
body.print-cert .palette,
body.print-cert .meta-btn {
  display: none !important;
}

/* ===== Раунд 4 ===== */

/* Избранное и метки на карточках */
.lesson-card { position: relative; }

.fav-star {
  position: absolute;
  top: 10px;
  right: 10px;
  z-index: 2;
  background: none;
  border: none;
  cursor: pointer;
  font-size: 19px;
  line-height: 1;
  opacity: 0.3;
  filter: grayscale(1);
  transition: opacity 0.2s, transform 0.2s;
  padding: 2px;
}

.fav-star:hover,
.fav-star.on {
  opacity: 1;
  filter: none;
}

.fav-star.on { transform: scale(1.08); }

.fav-hidden { display: none !important; }

.quiz-badge {
  position: absolute;
  right: 12px;
  bottom: 12px;
  font-size: 11px;
  font-weight: 700;
  color: var(--green);
  background: rgba(52, 211, 153, 0.12);
  border: 1px solid rgba(52, 211, 153, 0.3);
  padding: 2px 9px;
  border-radius: 999px;
}

.notes-flag {
  position: absolute;
  right: 12px;
  bottom: 40px;
  font-size: 13px;
  opacity: 0.9;
}

.fav-toggle {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  font-size: 14px;
  color: var(--muted);
  white-space: nowrap;
  cursor: pointer;
}

.fav-toggle input {
  accent-color: var(--accent);
  width: 16px;
  height: 16px;
  cursor: pointer;
}

/* Тосты и конфетти */
.toast {
  position: fixed;
  left: 50%;
  bottom: 28px;
  transform: translateX(-50%) translateY(16px);
  background: var(--card);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px 20px;
  box-shadow: var(--shadow);
  z-index: 150;
  font-size: 14px;
  opacity: 0;
  transition: opacity 0.3s, transform 0.3s;
  max-width: calc(100vw - 32px);
}

.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

.confetti-piece {
  position: fixed;
  top: -12px;
  z-index: 160;
  border-radius: 2px;
  pointer-events: none;
  animation: conf-fall linear forwards;
}

@keyframes conf-fall {
  to {
    transform: translateY(110vh) rotate(720deg);
    opacity: 0;
  }
}

/* Режим чтения и шрифт */
body.reading-mode .site-header,
body.reading-mode .site-footer,
body.reading-mode .sidebar,
body.reading-mode .lesson-nav,
body.reading-mode .lesson-meta,
body.reading-mode .next-lesson,
body.reading-mode .back-top,
body.reading-mode .lesson-notes,
body.reading-mode .kbd-hint,
body.reading-mode .toggle-wrap {
  display: none !important;
}

body.reading-mode .lesson-layout { display: block; }
body.reading-mode .lesson-body { max-width: 720px; margin: 0 auto; }
body.reading-mode .read-progress { z-index: 220; }

.read-mode-exit {
  position: fixed;
  top: 16px;
  right: 16px;
  z-index: 230;
  box-shadow: var(--shadow);
}

.font-label {
  font-size: 13px;
  color: var(--muted);
  min-width: 42px;
  text-align: center;
}

.kbd-hint {
  margin-left: auto;
  font-size: 11.5px;
  color: var(--muted);
  display: inline-flex;
  gap: 5px;
  flex-wrap: wrap;
  align-items: center;
}

.kbd-hint kbd {
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-bottom-width: 2px;
  border-radius: 5px;
  padding: 1px 6px;
  font-family: inherit;
  font-size: 11px;
  color: var(--text);
  white-space: nowrap;
}

/* Заметки к уроку */
.lesson-notes {
  margin-top: 28px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
  background: var(--card);
}

.lesson-notes h3 {
  font-size: 16px;
  margin: 0 0 10px;
}

.lesson-notes textarea {
  width: 100%;
  min-height: 110px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg-soft);
  color: var(--text);
  padding: 10px;
  font-family: inherit;
  font-size: 14px;
  resize: vertical;
  line-height: 1.5;
}

.notes-save-state {
  font-size: 12px;
  color: var(--muted);
  margin-top: 6px;
  min-height: 16px;
}

/* Глобальная статистика */
.gstat-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 12px;
}

.gstat {
  text-align: center;
  padding: 14px 10px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--bg-soft);
}

.gstat b {
  display: block;
  font-size: 22px;
  color: var(--accent);
  margin-bottom: 4px;
}

.gstat span {
  font-size: 12px;
  color: var(--muted);
}

/* Глоссарий */
.gloss-term {
  border-bottom: 1px dashed var(--accent);
  cursor: help;
}

.gloss-pop {
  position: fixed;
  max-width: 300px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px 14px;
  box-shadow: var(--shadow);
  z-index: 170;
  font-size: 13px;
}

.gloss-pop b {
  display: block;
  margin-bottom: 4px;
  color: var(--accent);
  font-size: 14px;
}

.gloss-pop p {
  margin: 0;
  line-height: 1.45;
  color: var(--text);
}

.gloss-dialog {
  position: fixed;
  inset: 0;
  z-index: 150;
  background: rgba(15, 23, 42, 0.6);
  display: none;
  padding: 14vh 16px 16px;
}

.gloss-dialog.show { display: block; }

.gloss-box {
  max-width: 520px;
  margin: 0 auto;
  background: var(--card);
  border-radius: 14px;
  border: 1px solid var(--border);
  overflow: hidden;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  max-height: 72vh;
}

.gloss-box input {
  padding: 14px 16px;
  border: none;
  border-bottom: 1px solid var(--border);
  background: transparent;
  color: var(--text);
  font: inherit;
  outline: none;
}

.gloss-list { overflow-y: auto; padding: 4px 14px 12px; }

.gloss-item {
  padding: 9px 4px;
  border-bottom: 1px solid var(--border);
}

.gloss-item:last-child { border-bottom: none; }

.gloss-item b { color: var(--accent); }

.gloss-item p {
  margin: 3px 0 0;
  font-size: 13px;
  line-height: 1.45;
  color: var(--text);
}

/* Печать: скрыть интерактив */
@media print {
  .toast,
  .confetti-piece,
  .gloss-pop,
  .gloss-dialog,
  .read-mode-exit,
  .kbd-hint,
  .fav-star,
  .notes-flag,
  .quiz-badge,
  .onboarding,
  .resume-btn,
  #installBtn,
  #certName,
  #dailyGoal,
  #yearMap,
  #globalStats {
    display: none !important;
  }
}

/* ===== Раунд 5 ===== */
.resume-btn {
  position: fixed;
  left: 16px;
  bottom: 24px;
  z-index: 140;
  box-shadow: var(--shadow);
}

.year-grid {
  display: grid;
  grid-template-columns: repeat(53, 1fr);
  gap: 3px;
  overflow-x: auto;
  padding-bottom: 6px;
}

.year-grid .act-cell {
  min-width: 10px;
}

.act-cell.lvl0 { background: var(--bg-soft); }
.act-cell.lvl1 { background: rgba(52, 211, 153, 0.25); }
.act-cell.lvl2 { background: rgba(52, 211, 153, 0.5); }
.act-cell.lvl3 { background: rgba(52, 211, 153, 0.75); }
.act-cell.lvl4 { background: #34d399; }

.onboarding {
  position: fixed;
  inset: 0;
  z-index: 250;
  background: rgba(15, 23, 42, 0.75);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
}

.ob-box {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  max-width: 420px;
  width: 100%;
  padding: 28px 26px;
  text-align: center;
  box-shadow: var(--shadow);
}

.ob-emoji { font-size: 44px; line-height: 1; }
.ob-title { margin: 12px 0 8px; font-size: 20px; color: var(--text); }
.ob-desc { font-size: 14px; color: var(--muted); line-height: 1.5; margin: 0; }

.ob-dots {
  display: flex;
  gap: 6px;
  justify-content: center;
  margin: 18px 0 14px;
}

.ob-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--border);
  transition: 0.2s;
}

.ob-dot.active {
  background: var(--accent);
  width: 22px;
  border-radius: 4px;
}

.ob-actions {
  display: flex;
  justify-content: center;
  gap: 10px;
}

/* ===== Тренировка квизов ===== */
.practice-top {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  margin-bottom: 18px;
}

#praCat {
  padding: 9px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg-soft);
  color: var(--text);
  font: inherit;
}

.practice-body {
  max-width: 680px;
  margin: 0 auto;
}

.pra-hint {
  text-align: center;
  color: var(--muted);
  font-size: 14px;
}

.pra-progress {
  font-size: 13px;
  color: var(--muted);
  margin-bottom: 8px;
  text-align: center;
}

.pra-lesson {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--accent);
  text-align: center;
  margin-bottom: 10px;
}

.pra-q {
  font-size: 18px;
  text-align: center;
  margin: 0 0 6px;
}

.pra-opt.right {
  border-color: #34d399;
  background: rgba(52, 211, 153, 0.15);
}

.pra-opt.wrong {
  border-color: #f87171;
  background: rgba(248, 113, 113, 0.15);
}

.pra-explain {
  min-height: 22px;
  font-size: 14px;
  color: #f87171;
  text-align: center;
  margin: 10px 0 0;
}

.pra-explain.ok {
  color: #34d399;
}

.pra-nav {
  text-align: center;
  margin-top: 14px;
}

.pra-result {
  text-align: center;
}

.pra-emoji {
  font-size: 46px;
  line-height: 1;
}

.pra-result h3 {
  margin: 10px 0 6px;
}

.pra-score {
  color: var(--muted);
  font-size: 15px;
}

.pra-actions {
  display: flex;
  gap: 10px;
  justify-content: center;
  flex-wrap: wrap;
  margin-top: 16px;
}

.btn-warn {
  border-color: #fbbf24;
  color: #fbbf24;
}