:root {
  --bg: #f7f5ef;
  --ink: #17211b;
  --muted: #5d675f;
  --line: #d9d2c2;
  --panel: #fffdf7;
  --panel-strong: #143d3a;
  --accent: #c84b31;
  --accent-2: #227c70;
  --gold: #c7982e;
  --code: #111827;
  --radius: 8px;
  --shadow: 0 22px 60px rgba(23, 33, 27, .10);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background:
    linear-gradient(120deg, rgba(34, 124, 112, .08), transparent 36%),
    linear-gradient(240deg, rgba(200, 75, 49, .08), transparent 34%),
    var(--bg);
  color: var(--ink);
}
a { color: inherit; }
.shell { width: min(1120px, calc(100% - 40px)); margin: 0 auto; }
.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(247, 245, 239, .88);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(18px);
}
.nav {
  min-height: 68px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}
.brand {
  font-family: "Source Serif 4", Georgia, serif;
  font-size: 25px;
  font-weight: 800;
  letter-spacing: -.02em;
  text-decoration: none;
}
.brand span { color: var(--accent); }
.nav-links { display: flex; align-items: center; gap: 18px; font-size: 14px; color: var(--muted); }
.nav-links a { text-decoration: none; }
.nav-links a:hover { color: var(--ink); }
.nav-cta {
  color: #fff !important;
  background: var(--ink);
  padding: 10px 14px;
  border-radius: var(--radius);
}
.hero {
  padding: 86px 0 54px;
  display: grid;
  grid-template-columns: minmax(0, 1.08fr) minmax(300px, .92fr);
  gap: 44px;
  align-items: end;
}
.eyebrow {
  color: var(--accent);
  font-size: 12px;
  font-weight: 800;
  letter-spacing: .12em;
  text-transform: uppercase;
}
h1, h2, h3 {
  font-family: "Source Serif 4", Georgia, serif;
  letter-spacing: -.035em;
  line-height: .98;
}
h1 {
  margin: 14px 0 20px;
  font-size: clamp(50px, 7.6vw, 92px);
  max-width: 820px;
}
h2 { margin: 0 0 16px; font-size: clamp(34px, 4vw, 54px); }
h3 { margin: 0 0 10px; font-size: 25px; }
p { line-height: 1.7; }
.hero-copy {
  max-width: 720px;
  font-size: 19px;
  color: var(--muted);
}
.actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 28px; }
.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 12px 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  color: var(--ink);
  font-weight: 800;
  text-decoration: none;
}
.button.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.button.dark { background: var(--ink); border-color: var(--ink); color: #fff; }
.summary-card {
  background: var(--panel-strong);
  color: #f5fbf8;
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: var(--shadow);
}
.summary-card p { color: rgba(245, 251, 248, .78); margin: 0; }
.summary-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  border-top: 1px solid rgba(255, 255, 255, .16);
  margin-top: 24px;
  padding-top: 20px;
  gap: 16px;
}
.summary-grid b { display: block; font-size: 30px; font-family: "Source Serif 4", Georgia, serif; }
.summary-grid span { color: rgba(245, 251, 248, .72); font-size: 12px; text-transform: uppercase; letter-spacing: .08em; }
section { padding: 66px 0; }
.band { border-top: 1px solid var(--line); }
.grid { display: grid; gap: 18px; }
.grid.two { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid.three { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.card {
  background: rgba(255, 253, 247, .82);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px;
}
.card.dark { background: var(--ink); color: #fff; border-color: var(--ink); }
.card.dark p, .card.dark li { color: rgba(255, 255, 255, .72); }
.card p { margin: 0; color: var(--muted); }
.phase-card { display: grid; grid-template-rows: auto 1fr auto; min-height: 300px; }
.phase-meta {
  display: flex;
  justify-content: space-between;
  gap: 14px;
  color: var(--accent-2);
  font-size: 12px;
  font-weight: 900;
  letter-spacing: .08em;
  text-transform: uppercase;
  margin-bottom: 18px;
}
.phase-card ul, .content-list {
  display: grid;
  gap: 9px;
  margin: 16px 0 20px;
  padding-left: 18px;
  color: var(--muted);
  line-height: 1.55;
}
.phase-card a { font-weight: 900; color: var(--accent); text-decoration: none; }
.roadmap {
  position: relative;
  display: grid;
  gap: 14px;
}
.roadmap-item {
  display: grid;
  grid-template-columns: 108px 1fr;
  gap: 18px;
  align-items: start;
  padding: 18px;
  background: rgba(255, 253, 247, .78);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}
.roadmap-item strong { color: var(--accent-2); }
.roadmap-item p { margin: 4px 0 0; color: var(--muted); }
.page-layout {
  display: grid;
  grid-template-columns: 260px minmax(0, 1fr);
  gap: 34px;
  padding: 42px 0 80px;
}
.side-nav {
  position: sticky;
  top: 92px;
  align-self: start;
  display: grid;
  gap: 8px;
  padding: 16px;
  background: rgba(255, 253, 247, .8);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}
.side-nav a {
  color: var(--muted);
  text-decoration: none;
  font-size: 14px;
  padding: 8px;
  border-radius: 6px;
}
.side-nav a:hover { color: var(--ink); background: rgba(34, 124, 112, .08); }
.lesson {
  background: rgba(255, 253, 247, .82);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px;
  margin-bottom: 18px;
}
.lesson h2 { font-size: clamp(30px, 3vw, 44px); }
.checklist {
  display: grid;
  gap: 10px;
  margin: 18px 0 0;
  padding: 0;
  list-style: none;
}
.checklist li {
  display: grid;
  grid-template-columns: 24px 1fr;
  gap: 10px;
  color: var(--muted);
  line-height: 1.55;
}
.checklist li::before {
  content: "";
  width: 14px;
  height: 14px;
  border: 2px solid var(--accent-2);
  border-radius: 4px;
  margin-top: 4px;
}
.code-card {
  background: var(--code);
  color: #d1fae5;
  border-radius: var(--radius);
  padding: 18px;
  overflow: auto;
  font-family: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 13px;
  line-height: 1.6;
}
.table {
  width: 100%;
  border-collapse: collapse;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}
.table th, .table td {
  padding: 14px;
  border-bottom: 1px solid var(--line);
  text-align: left;
  vertical-align: top;
}
.table th { background: rgba(34, 124, 112, .09); }
.table tr:last-child td { border-bottom: 0; }
.callout {
  border-left: 4px solid var(--accent);
  background: rgba(200, 75, 49, .08);
  padding: 16px;
  border-radius: 0 var(--radius) var(--radius) 0;
  color: var(--muted);
}
.ladder-visual {
  display: grid;
  gap: 10px;
  margin-top: 24px;
}
.ladder-step {
  display: grid;
  grid-template-columns: 34px 1fr;
  gap: 12px;
  align-items: center;
  padding: 10px;
  border: 1px solid rgba(255, 255, 255, .14);
  border-radius: var(--radius);
  background: rgba(255, 255, 255, .08);
}
.ladder-step b {
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  border-radius: 50%;
  background: #f5fbf8;
  color: var(--panel-strong);
}
.ladder-step span { color: rgba(245, 251, 248, .78); font-size: 14px; }
.visual-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 18px;
  margin-top: 22px;
}
.visual-card {
  min-height: 230px;
  display: grid;
  align-items: end;
  background: #fffdf7;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px;
  overflow: hidden;
}
.visual-card h3 { font-size: 21px; margin-top: 16px; }
.visual-card p { margin: 0; color: var(--muted); font-size: 14px; }
.phone-mock {
  width: min(100%, 260px);
  margin: 0 auto 16px;
  padding: 12px;
  border: 8px solid #1f2937;
  border-radius: 30px;
  background: #f8fafc;
  box-shadow: 0 16px 38px rgba(15, 23, 42, .18);
}
.phone-mock.wide {
  width: min(100%, 420px);
  border-radius: 24px;
}
.mock-bar {
  height: 18px;
  border-radius: 999px;
  background: #0f766e;
  margin-bottom: 12px;
}
.mock-title {
  width: 58%;
  height: 16px;
  border-radius: 999px;
  background: #17211b;
  margin-bottom: 14px;
}
.mock-row {
  display: grid;
  grid-template-columns: 34px 1fr 46px;
  gap: 10px;
  align-items: center;
  padding: 10px;
  border-radius: 12px;
  background: #eef2f1;
  margin-bottom: 8px;
}
.mock-dot { width: 30px; height: 30px; border-radius: 50%; background: #c84b31; }
.mock-line, .mock-pill { height: 10px; border-radius: 999px; background: #94a3b8; }
.mock-pill { background: #227c70; }
.mock-tabs {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  margin: 12px 0;
}
.mock-tabs span {
  height: 26px;
  border-radius: 999px;
  background: #dbe7e4;
}
.mock-tabs span:first-child { background: #c84b31; }
.mock-card {
  min-height: 86px;
  border-radius: 16px;
  background: linear-gradient(135deg, #f7d88a, #f5f0df);
  padding: 12px;
}
.mock-card::before, .mock-card::after {
  content: "";
  display: block;
  height: 10px;
  border-radius: 999px;
  background: rgba(23, 33, 27, .38);
  margin-bottom: 10px;
}
.mock-card::after { width: 55%; }
.diagram-visual {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
  align-items: stretch;
  margin: 18px 0;
}
.diagram-node {
  display: grid;
  place-items: center;
  min-height: 78px;
  padding: 12px;
  border-radius: var(--radius);
  background: #e9f3ef;
  border: 1px solid #bdd6cd;
  text-align: center;
  font-weight: 800;
  color: #143d3a;
}
.diagram-node.hot {
  background: #f9eadc;
  border-color: #edc1a9;
  color: #9d321e;
}
.metric-board {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  margin: 18px 0;
}
.metric-tile {
  min-height: 96px;
  padding: 14px;
  border-radius: var(--radius);
  background: #17211b;
  color: #fff;
}
.metric-tile b {
  display: block;
  font-family: "Source Serif 4", Georgia, serif;
  font-size: 30px;
}
.metric-tile span { color: rgba(255, 255, 255, .68); font-size: 13px; }
.strategy-map {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin: 18px 0;
}
.strategy-map div {
  min-height: 112px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 14px;
  background: #fffdf7;
}
.strategy-map b { display: block; margin-bottom: 8px; }
.strategy-map span { color: var(--muted); font-size: 14px; line-height: 1.55; }
.lesson-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
  margin-top: 22px;
}
.tutorial-card {
  display: grid;
  grid-template-columns: 56px 1fr;
  gap: 14px;
  padding: 16px;
  background: #fffdf7;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  text-decoration: none;
}
.tutorial-card:hover { border-color: var(--accent-2); }
.tutorial-card b {
  display: grid;
  place-items: center;
  width: 44px;
  height: 44px;
  border-radius: 12px;
  background: #e8f2ef;
  color: var(--accent-2);
}
.tutorial-card h3 { font-size: 21px; margin: 0 0 6px; }
.tutorial-card p { margin: 0; color: var(--muted); font-size: 14px; }
.concept-visual {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  margin: 18px 0;
}
.concept-box {
  min-height: 110px;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fffdf7;
}
.concept-box b { display: block; margin-bottom: 8px; }
.concept-box span { color: var(--muted); font-size: 14px; line-height: 1.55; }
.ide-visual {
  display: grid;
  grid-template-columns: 150px 1fr;
  min-height: 260px;
  margin: 18px 0;
  border: 8px solid #17211b;
  border-radius: 18px;
  background: #111827;
  overflow: hidden;
}
.ide-sidebar { background: #1f2937; padding: 12px; display: grid; gap: 8px; align-content: start; }
.ide-sidebar span { height: 18px; border-radius: 6px; background: #475569; }
.ide-editor { padding: 14px; display: grid; gap: 10px; align-content: start; }
.ide-line { height: 12px; border-radius: 999px; background: #64748b; }
.ide-line.short { width: 48%; }
.ide-line.mid { width: 72%; }
.ide-line.hot { background: #34d399; width: 64%; }
.ui-tree { display: grid; gap: 10px; margin: 18px 0; }
.tree-node {
  padding: 12px;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: #fffdf7;
  font-weight: 800;
}
.tree-node.child { margin-left: 34px; background: #edf7f4; }
.tree-node.leaf { margin-left: 68px; background: #f9eadc; }
.debug-panel {
  display: grid;
  gap: 10px;
  margin: 18px 0;
  padding: 16px;
  border-radius: var(--radius);
  background: #111827;
  color: #d1fae5;
  font-family: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 13px;
}
.debug-panel span { color: #fca5a5; }
.quiz-shell { display: grid; gap: 18px; }
.quiz-card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fffdf7;
  padding: 18px;
}
.quiz-option {
  display: block;
  margin: 10px 0;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #f8f4e9;
  cursor: pointer;
}
.quiz-option input { margin-right: 8px; }
.drop-zone {
  display: grid;
  gap: 10px;
  min-height: 210px;
  padding: 12px;
  border: 2px dashed #bdd6cd;
  border-radius: var(--radius);
  background: #edf7f4;
}
.drag-item {
  padding: 12px;
  border-radius: var(--radius);
  background: #17211b;
  color: #fff;
  cursor: grab;
  user-select: none;
}
.drag-item.dragging { opacity: .45; }
.drag-item.selected {
  outline: 3px solid var(--gold);
  outline-offset: 2px;
}
.quiz-actions { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 12px; }
.quiz-feedback {
  min-height: 26px;
  margin-top: 10px;
  color: var(--accent-2);
  font-weight: 800;
}
.match-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}
.match-grid select {
  width: 100%;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fff;
}
.source-note {
  margin-top: 18px;
  font-size: 14px;
  color: var(--muted);
}
.file-tree {
  display: grid;
  gap: 6px;
  margin: 18px 0;
  padding: 16px;
  border-radius: var(--radius);
  background: #17211b;
  color: #d1fae5;
  font-family: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 13px;
  line-height: 1.6;
}
.step-label {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 5px 9px;
  border-radius: 999px;
  background: #e8f2ef;
  color: var(--accent-2);
  font-size: 12px;
  font-weight: 900;
  letter-spacing: .08em;
  text-transform: uppercase;
}
.error-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin-top: 16px;
}
.error-card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fffdf7;
  padding: 14px;
}
.error-card b { display: block; margin-bottom: 8px; color: #9d321e; }
.error-card span { color: var(--muted); font-size: 14px; line-height: 1.55; }
.tutorial-flow {
  display: grid;
  gap: 18px;
  counter-reset: tutorial-step;
}
.tutorial-step {
  position: relative;
  display: grid;
  gap: 14px;
  padding: 24px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fffdf7;
}
.tutorial-step::before {
  counter-increment: tutorial-step;
  content: counter(tutorial-step, decimal-leading-zero);
  display: grid;
  place-items: center;
  width: 46px;
  height: 46px;
  border-radius: 14px;
  background: var(--ink);
  color: #fff;
  font-weight: 900;
}
.tutorial-step h2 {
  margin-top: -58px;
  margin-left: 64px;
  font-size: clamp(28px, 3vw, 42px);
}
.tutorial-step > p,
.tutorial-step > .content-list,
.tutorial-step > .code-card,
.tutorial-step > .table,
.tutorial-step > .callout,
.tutorial-step > .phone-mock,
.tutorial-step > .diagram-visual,
.tutorial-step > .error-grid,
.tutorial-step > .file-tree {
  margin-left: 64px;
}
.expected-result {
  margin-left: 64px;
  padding: 14px;
  border-left: 4px solid var(--accent-2);
  border-radius: 0 var(--radius) var(--radius) 0;
  background: #edf7f4;
  color: var(--muted);
}
.checkpoint-box {
  margin-left: 64px;
  padding: 14px;
  border: 1px solid #edc1a9;
  border-radius: var(--radius);
  background: #f9eadc;
}
.checkpoint-box b { display: block; margin-bottom: 8px; color: #9d321e; }
.footer {
  border-top: 1px solid var(--line);
  padding: 30px 0;
  color: var(--muted);
  font-size: 14px;
}
.footer .shell { display: flex; justify-content: space-between; gap: 18px; flex-wrap: wrap; }
.footer a { margin-left: 16px; text-decoration: none; }

@media (max-width: 860px) {
  .nav { align-items: flex-start; padding: 16px 0; flex-direction: column; }
  .nav-links { flex-wrap: wrap; }
  .hero, .grid.two, .grid.three, .page-layout, .visual-grid, .diagram-visual, .metric-board, .strategy-map, .lesson-grid, .concept-visual, .ide-visual, .match-grid, .error-grid { grid-template-columns: 1fr; }
  .side-nav { position: static; }
  .summary-grid { grid-template-columns: 1fr; }
  .roadmap-item { grid-template-columns: 1fr; }
  section { padding: 48px 0; }
}

@media (max-width: 560px) {
  .shell { width: min(100% - 28px, 1120px); }
  h1 { font-size: 46px; }
  .hero { padding-top: 56px; }
  .nav-links a:not(.nav-cta) { display: none; }
  .lesson, .card, .summary-card { padding: 20px; }
  .tutorial-step h2,
  .tutorial-step > p,
  .tutorial-step > .content-list,
  .tutorial-step > .code-card,
  .tutorial-step > .table,
  .tutorial-step > .callout,
  .tutorial-step > .phone-mock,
  .tutorial-step > .diagram-visual,
  .tutorial-step > .error-grid,
  .tutorial-step > .file-tree,
  .expected-result,
  .checkpoint-box { margin-left: 0; }
  .tutorial-step h2 { margin-top: 0; }
}