/* ============ Reset & Base ============ */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  background: linear-gradient(135deg, #FFF5E6 0%, #FFFAF2 40%, #FFE5F2 100%);
  color: #1A1A1A;
  line-height: 1.7;
  min-height: 100vh;
}

img,
svg,
video,
canvas {
  max-width: 100%;
  display: block;
  height: auto;
}

ul,
ol {
  list-style: none;
}

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

button {
  font: inherit;
  border: none;
  background: none;
  cursor: pointer;
  color: inherit;
}

:focus-visible {
  outline: 3px solid #FFD700;
  outline-offset: 3px;
  border-radius: 6px;
}

/* ============ CSS Variables ============ */
:root {
  --peach: #FF99CC;
  --peach-light: #FFB8D5;
  --peach-deep: #FF6B9E;
  --peach-dark: #E84A7A;
  --peach-grad: linear-gradient(135deg, #FFB8D5, #FF6B9E);
  --purple: #2D1B4E;
  --purple-dark: #1E1033;
  --purple-black: #150A2A;
  --gold: #FFD700;
  --paper: #FFF5E6;
  --paper-light: #FFFAF2;
  --ink: #1A1A1A;
  --peach-card: #FFE5F2;
  --peach-border: #FFD0E8;
  --white: #FFFFFF;
  --font-heading: "ZCOOL KuaiLe", "Ma Shan Zheng", "Noto Sans SC", sans-serif;
  --font-body: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-number: "Georgia", "Times New Roman", "Noto Serif SC", serif;
  --container-w: 1240px;
  --radius-lg: 32px;
  --radius-md: 20px;
  --radius-sm: 12px;
  --shadow-soft: 0 12px 40px rgba(45, 27, 78, 0.10);
  --shadow-peach: 0 8px 32px rgba(255, 107, 158, 0.24);
  --space-1: 0.5rem;
  --space-2: 1rem;
  --space-3: 1.5rem;
  --space-4: 2rem;
  --space-5: 3rem;
  --space-6: 4.5rem;
  --space-7: 6rem;
  --transition-fast: 150ms ease;
  --transition-base: 260ms cubic-bezier(0.22, 0.61, 0.36, 1);
}

/* ============ Skip Link ============ */
.skip-link {
  position: fixed;
  top: -100px;
  left: 16px;
  z-index: 2000;
  background: var(--purple);
  color: var(--gold);
  padding: 12px 24px;
  border-radius: 0 0 12px 12px;
  font-weight: 700;
  transition: top var(--transition-fast);
}

.skip-link:focus-visible {
  top: 0;
}

/* ============ Header ============ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: var(--peach-grad);
  border-bottom: 3px solid var(--purple);
  box-shadow: 0 4px 24px rgba(45, 27, 78, 0.10);
}

.header-shell {
  max-width: var(--container-w);
  margin: 0 auto;
  padding: 0 var(--space-3);
  display: flex;
  align-items: center;
  gap: var(--space-4);
  min-height: 78px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-shrink: 0;
  transition: transform var(--transition-fast);
}

.brand:hover {
  transform: scale(1.02);
}

.brand:active {
  transform: scale(0.97);
}

.brand-mark,
.footer-mark {
  display: block;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: radial-gradient(circle at 34% 30%, #FFE6F0 0%, #FFB8D5 45%, var(--peach-deep) 100%);
  border: 2px solid var(--purple);
  position: relative;
  box-shadow: inset 0 -4px 8px rgba(45, 27, 78, 0.10), 0 4px 12px rgba(255, 107, 158, 0.35);
}

.brand-mark::before,
.footer-mark::before {
  content: "";
  position: absolute;
  width: 18px;
  height: 18px;
  top: 8px;
  left: 14px;
  border-radius: 50% 50% 50% 4px;
  background: linear-gradient(135deg, #ffffff 0%, #FFD0E8 70%);
  opacity: 0.9;
  transform: rotate(-18deg);
}

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.1;
}

.brand-name {
  font-family: var(--font-heading);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--purple);
  letter-spacing: 0.04em;
}

.brand-badge {
  font-size: 0.7rem;
  letter-spacing: 0.12em;
  color: var(--purple);
  background: var(--gold);
  padding: 2px 10px;
  border-radius: 999px;
  align-self: flex-start;
  font-weight: 700;
  margin-top: 3px;
}

/* ============ Navigation ============ */
.site-nav {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-left: auto;
}

.nav-link {
  font-size: 0.92rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--purple);
  background: rgba(255, 255, 255, 0.12);
  border: 2px solid transparent;
  border-radius: 999px;
  padding: 0.55rem 1rem;
  line-height: 1;
  transition: background var(--transition-fast), color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.nav-link:hover {
  background: var(--purple);
  color: var(--peach-light);
  border-color: var(--gold);
  box-shadow: 0 4px 14px rgba(45, 27, 78, 0.25);
}

.nav-link[aria-current="page"] {
  background: var(--purple);
  color: var(--gold);
  border-color: var(--gold);
  box-shadow: 0 6px 0 rgba(45, 27, 78, 0.18);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 6px;
  margin-left: auto;
  width: 52px;
  height: 52px;
  border-radius: 50%;
  background: var(--purple);
  color: var(--gold);
  border: 2px solid var(--gold);
  box-shadow: 0 6px 16px rgba(45, 27, 78, 0.25);
  transition: transform var(--transition-fast), background var(--transition-fast);
}

.nav-toggle:hover {
  transform: scale(1.08);
  background: var(--purple-dark);
}

.nav-toggle:active {
  transform: scale(0.94);
}

.nav-toggle-box {
  width: 22px;
  height: 2px;
  background: var(--gold);
  border-radius: 2px;
  position: relative;
  transition: background var(--transition-fast);
  display: block;
}

.nav-toggle-box::before,
.nav-toggle-box::after {
  content: "";
  position: absolute;
  left: 0;
  width: 22px;
  height: 2px;
  background: var(--gold);
  border-radius: 2px;
  transition: transform var(--transition-base), top var(--transition-base);
}

.nav-toggle-box::before {
  top: -8px;
}

.nav-toggle-box::after {
  top: 8px;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-box {
  background: transparent;
}

.nav-toggle[aria-expanded="true"] .nav-toggle-box::before {
  top: 0;
  transform: rotate(45deg);
}

.nav-toggle[aria-expanded="true"] .nav-toggle-box::after {
  top: 0;
  transform: rotate(-45deg);
}

.nav-toggle-label {
  font-size: 0.6rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  margin-top: 4px;
}

/* ============ Footer ============ */
.site-footer {
  background: var(--purple-dark);
  color: var(--peach-light);
  border-top: 4px solid var(--peach-deep);
  margin-top: var(--space-6);
  position: relative;
  overflow: hidden;
}

.site-footer::before {
  content: "";
  position: absolute;
  top: 0;
  right: -80px;
  width: 300px;
  height: 300px;
  background: radial-gradient(circle at center, rgba(255, 107, 158, 0.18) 0%, rgba(255, 107, 158, 0) 70%);
  pointer-events: none;
}

.site-footer::after {
  content: "";
  position: absolute;
  bottom: -60px;
  left: -60px;
  width: 260px;
  height: 260px;
  border-radius: 50%;
  background: radial-gradient(circle at center, rgba(255, 215, 0, 0.10) 0%, rgba(255, 215, 0, 0) 70%);
  pointer-events: none;
}

.footer-shell {
  max-width: var(--container-w);
  margin: 0 auto;
  padding: var(--space-6) var(--space-3) var(--space-4);
  position: relative;
  z-index: 1;
}

.footer-brand {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  max-width: 480px;
  margin-bottom: var(--space-5);
  padding-bottom: var(--space-3);
  border-bottom: 2px solid rgba(255, 153, 204, 0.35);
}

.footer-mark {
  border-color: var(--gold);
  box-shadow: 0 0 24px rgba(255, 215, 0, 0.25);
}

.footer-brand-name {
  font-family: var(--font-heading);
  font-size: 1.8rem;
  color: var(--gold);
  letter-spacing: 0.06em;
}

.footer-trust {
  font-size: 0.9rem;
  line-height: 1.7;
  color: rgba(255, 230, 242, 0.85);
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-4);
  margin-bottom: var(--space-5);
}

.footer-col h2 {
  font-family: var(--font-heading);
  font-size: 1rem;
  letter-spacing: 0.14em;
  color: var(--gold);
  margin-bottom: var(--space-2);
  padding-bottom: 8px;
  border-bottom: 2px dotted rgba(255, 153, 204, 0.4);
}

.footer-nav {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.footer-nav a {
  font-size: 0.9rem;
  color: rgba(255, 230, 242, 0.9);
  padding: 4px 0;
  border-bottom: 2px solid transparent;
  transition: color var(--transition-fast), border-color var(--transition-fast), padding-left var(--transition-fast);
}

.footer-nav a:hover {
  color: var(--gold);
  border-bottom-color: var(--peach-deep);
  padding-left: 6px;
}

.footer-contact p {
  font-size: 0.88rem;
  line-height: 1.7;
  color: rgba(255, 230, 242, 0.9);
  margin-bottom: 6px;
}

.footer-contact a {
  color: var(--peach-light);
  font-weight: 700;
  border-bottom: 2px solid rgba(255, 153, 204, 0.4);
  padding-bottom: 1px;
  transition: color var(--transition-fast), border-color var(--transition-fast);
}

.footer-contact a:hover {
  color: var(--gold);
  border-color: var(--gold);
}

.footer-legal {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-4);
  padding-top: var(--space-3);
  border-top: 2px solid rgba(255, 153, 204, 0.3);
  font-size: 0.82rem;
  color: rgba(255, 230, 242, 0.65);
}

.footer-legal a {
  color: rgba(255, 230, 242, 0.8);
  border-bottom: 1px solid rgba(255, 215, 0, 0.4);
  transition: color var(--transition-fast), border-color var(--transition-fast);
}

.footer-legal a:hover {
  color: var(--gold);
  border-color: var(--gold);
}

/* ============ Common Page Utilities ============ */
#main-content {
  display: block;
}

.page-caption {
  max-width: var(--container-w);
  margin: var(--space-5) auto var(--space-4);
  padding: var(--space-3);
  background: var(--paper);
  border-left: 8px solid var(--peach-deep);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  box-shadow: var(--shadow-soft);
}

.page-caption h1 {
  font-family: var(--font-heading);
  font-size: 2rem;
  color: var(--purple);
  letter-spacing: 0.04em;
}

.page-caption p {
  color: rgba(26, 26, 26, 0.8);
  font-size: 0.92rem;
  margin-top: 6px;
}

.breadcrumbs {
  max-width: var(--container-w);
  margin: var(--space-4) auto 0;
  padding: 0 var(--space-3);
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--peach-dark);
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.breadcrumbs a {
  color: var(--purple);
  border-bottom: 2px solid rgba(232, 74, 122, 0.35);
  transition: color var(--transition-fast), border-color var(--transition-fast);
}

.breadcrumbs a:hover {
  color: var(--peach-dark);
  border-color: var(--peach-dark);
}

.breadcrumbs [aria-current="page"] {
  color: var(--peach-dark);
  border-bottom: none;
}

.prose-body {
  max-width: 780px;
  margin: 0 auto;
  padding: var(--space-4) var(--space-3);
  font-size: 1rem;
  line-height: 1.8;
  color: var(--ink);
}

.prose-body h2 {
  font-family: var(--font-heading);
  font-size: 1.45rem;
  color: var(--purple);
  margin-top: var(--space-5);
  margin-bottom: var(--space-2);
  padding-bottom: 8px;
  border-bottom: 4px solid;
  border-image: linear-gradient(90deg, var(--gold), var(--peach-deep)) 1;
}

.prose-body h3 {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  color: var(--peach-dark);
  margin-top: var(--space-4);
  margin-bottom: var(--space-2);
  padding-left: 12px;
  border-left: 4px solid var(--peach-deep);
}

.prose-body p {
  margin-bottom: var(--space-2);
}

.prose-body ul {
  list-style: disc;
  padding-left: 1.5em;
  margin-bottom: var(--space-2);
}

.prose-body ol {
  list-style: decimal;
  padding-left: 1.5em;
  margin-bottom: var(--space-2);
}

.prose-body li {
  margin-bottom: 0.35rem;
}

.prose-body a {
  color: var(--peach-dark);
  font-weight: 700;
  border-bottom: 2px solid rgba(232, 74, 122, 0.35);
  transition: color var(--transition-fast), border-color var(--transition-fast);
}

.prose-body a:hover {
  color: var(--purple);
  border-color: var(--purple);
}

.prose-body strong {
  color: var(--purple);
  font-weight: 800;
}

.prose-body blockquote {
  border-left: 6px solid var(--gold);
  background: rgba(255, 215, 0, 0.12);
  padding: var(--space-2) var(--space-3);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: var(--space-3) 0;
}

/* ============ Section Heading (chapter labels) ============ */
.chapter-label {
  font-family: var(--font-heading);
  font-size: 0.9rem;
  letter-spacing: 0.2em;
  color: var(--peach-dark);
  background: var(--peach-card);
  display: inline-block;
  padding: 4px 14px;
  border-radius: 999px;
  border: 2px solid var(--peach-border);
  margin-bottom: var(--space-2);
}

.chapter-title {
  font-family: var(--font-heading);
  font-size: 2rem;
  line-height: 1.15;
  color: var(--purple);
  letter-spacing: 0.02em;
  margin-bottom: var(--space-2);
}

.chapter-deck {
  font-size: 0.95rem;
  color: rgba(26, 26, 26, 0.78);
  max-width: 60ch;
}

/* ============ Category Tabs (reusable) ============ */
.tab-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: var(--space-4);
}

.tab-item {
  background: var(--peach-card);
  border: 2px solid var(--peach-border);
  border-radius: 999px;
  padding: 8px 18px;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--purple);
  transition: background var(--transition-fast), color var(--transition-fast), transform var(--transition-fast), border-color var(--transition-fast);
}

.tab-item:hover {
  background: var(--peach-deep);
  color: var(--white);
  border-color: var(--peach-deep);
  transform: translateY(-2px);
}

.tab-item[aria-selected="true"] {
  background: var(--purple);
  color: var(--gold);
  border-color: var(--gold);
  box-shadow: 0 4px 14px rgba(45, 27, 78, 0.25);
}

/* ============ Cards / Grid ============ */
.grid-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-4);
  max-width: var(--container-w);
  margin: 0 auto;
  padding: 0 var(--space-3);
}

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

.grid-cards.four-col {
  grid-template-columns: repeat(4, 1fr);
}

.card {
  background: var(--paper);
  border: 3px solid var(--peach-border);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
  transition: box-shadow var(--transition-base), transform var(--transition-base), border-color var(--transition-base);
  position: relative;
  overflow: hidden;
}

.card::before {
  content: "";
  position: absolute;
  top: -32px;
  right: -32px;
  width: 90px;
  height: 90px;
  border-radius: 50%;
  background: rgba(255, 153, 204, 0.22);
  transition: transform var(--transition-base);
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-peach);
  border-color: var(--peach-deep);
}

.card:hover::before {
  transform: scale(1.4);
}

.card-accent {
  font-family: var(--font-number);
  font-size: 1.6rem;
  font-weight: 800;
  color: var(--peach-dark);
  background: var(--peach-card);
  display: inline-block;
  padding: 4px 14px;
  border-radius: 999px;
  margin-bottom: var(--space-2);
}

.card-accent.gold {
  background: rgba(255, 215, 0, 0.2);
  color: #B8860B;
}

.card-title {
  font-family: var(--font-heading);
  font-size: 1.1rem;
  color: var(--purple);
  margin-bottom: 6px;
}

.card-desc {
  font-size: 0.88rem;
  color: rgba(26, 26, 26, 0.78);
  line-height: 1.55;
}

.card-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-top: var(--space-2);
  font-weight: 700;
  font-size: 0.85rem;
  color: var(--peach-dark);
  transition: gap var(--transition-fast), color var(--transition-fast);
}

.card-link::after {
  content: "→";
  font-size: 1.1rem;
  transition: transform var(--transition-fast);
}

.card-link:hover {
  color: var(--purple);
  gap: 12px;
}

.card-link:hover::after {
  transform: translateX(3px);
}

/* ============ Collapsible Panels ============ */
.collapsible-box {
  background: var(--paper);
  border: 3px solid var(--peach-border);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-2);
  overflow: hidden;
  transition: border-color var(--transition-fast);
}

.collapsible-box:has([data-collapse-toggle][aria-expanded="true"]) {
  border-color: var(--peach-deep);
}

.collapse-toggle-row {
  width: 100%;
  text-align: left;
  padding: var(--space-2) var(--space-3);
  display: flex;
  align-items: center;
  gap: 12px;
  font-weight: 700;
  color: var(--purple);
  background: linear-gradient(90deg, rgba(255, 229, 242, 0.9), rgba(255, 245, 230, 0.9));
  cursor: pointer;
  transition: background var(--transition-fast);
}

.collapse-toggle-row:hover {
  background: var(--peach-card);
}

.collapse-indicator {
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: var(--purple);
  color: var(--gold);
  display: grid;
  place-items: center;
  font-size: 0.9rem;
  flex-shrink: 0;
  transition: transform var(--transition-base);
}

.collapse-toggle-row[aria-expanded="true"] .collapse-indicator {
  transform: rotate(45deg);
  background: var(--peach-deep);
}

.collapse-panel {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition-base), padding var(--transition-base);
}

.collapse-panel-inner {
  padding: 0 var(--space-4);
  font-size: 0.9rem;
  color: var(--ink);
  line-height: 1.75;
  border-top: 2px dashed var(--peach-border);
}

.collapse-toggle-row[aria-expanded="true"] + .collapse-panel {
  max-height: 40rem;
}

.collapse-toggle-row[aria-expanded="true"] + .collapse-panel .collapse-panel-inner {
  padding-top: var(--space-3);
  padding-bottom: var(--space-3);
}

/* ============ Table of Contents (preview strips) ============ */
.toc-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.toc-item {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  background: var(--paper);
  border: 2px solid var(--peach-border);
  border-radius: var(--radius-md);
  padding: var(--space-2) var(--space-3);
  transition: transform var(--transition-base), box-shadow var(--transition-base), background var(--transition-fast), border-color var(--transition-fast);
}

.toc-item:hover {
  transform: translateX(8px);
  box-shadow: var(--shadow-soft);
  border-color: var(--peach-deep);
  background: var(--paper-light);
}

.toc-index {
  font-family: var(--font-number);
  font-weight: 800;
  font-size: 1.3rem;
  color: var(--gold);
  background: var(--purple);
  width: 46px;
  height: 46px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  flex-shrink: 0;
}

.toc-content .section-title-line {
  font-family: var(--font-heading);
  color: var(--purple);
  font-size: 1.05rem;
  margin-bottom: 2px;
}

.toc-content p {
  font-size: 0.82rem;
  color: rgba(26, 26, 26, 0.7);
  line-height: 1.45;
}

.toc-link-meta {
  margin-left: auto;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--peach-dark);
  background: var(--peach-card);
  padding: 4px 12px;
  border-radius: 999px;
  white-space: nowrap;
  border: 1px solid var(--peach-border);
}

/* ============ Image Placeholder Canvas ============ */
.image-canvas {
  position: relative;
  width: 100%;
  aspect-ratio: 4 / 3;
  border-radius: var(--radius-md);
  overflow: hidden;
  background: linear-gradient(145deg, #FFD0E8 0%, #FFB8D5 48%, #FF6B9E 100%);
  display: grid;
  place-items: center;
  border: 3px solid var(--peach-border);
  box-shadow: inset 0 0 0 6px rgba(255, 255, 255, 0.25);
}

.image-canvas::before {
  content: "IMAGE SLOT";
  font-family: var(--font-heading);
  font-size: 0.9rem;
  font-weight: 700;
  letter-spacing: 0.2em;
  color: rgba(45, 27, 78, 0.6);
  background: rgba(255, 255, 255, 0.55);
  padding: 6px 18px;
  border-radius: 999px;
}

.image-canvas.is-wide {
  aspect-ratio: 16 / 9;
}

.image-canvas.is-tall {
  aspect-ratio: 3 / 4;
}

.image-canvas.is-round {
  border-radius: 50%;
  aspect-ratio: 1 / 1;
}

/* ============ Back to Top ============ */
.back-to-top {
  position: fixed;
  right: 24px;
  bottom: 24px;
  z-index: 900;
  width: 52px;
  height: 52px;
  border-radius: 50%;
  background: var(--purple);
  color: var(--gold);
  border: 3px solid var(--gold);
  font-size: 1.2rem;
  opacity: 0;
  visibility: hidden;
  transform: translateY(16px);
  transition: opacity var(--transition-base), transform var(--transition-base), visibility var(--transition-base), background var(--transition-fast);
  box-shadow: 0 8px 24px rgba(45, 27, 78, 0.35);
  display: grid;
  place-items: center;
}

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

.back-to-top:hover {
  background: var(--peach-deep);
  transform: scale(1.08) translateY(0);
}

.back-to-top:active {
  transform: scale(0.95);
}

/* ============ Scroll Progress ============ */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 5px;
  width: 0%;
  background: linear-gradient(90deg, var(--gold), var(--peach-deep));
  z-index: 2000;
  border-radius: 0 3px 3px 0;
  box-shadow: 0 2px 6px rgba(255, 107, 158, 0.4);
  pointer-events: none;
}

/* ============ Responsive ============ */

@media (max-width: 1024px) {
  .header-shell {
    padding: 0 var(--space-2);
    gap: var(--space-2);
  }

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

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

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

@media (max-width: 820px) {
  .nav-toggle {
    display: flex;
  }

  .site-nav {
    display: none;
    position: fixed;
    top: 78px;
    left: 12px;
    right: 12px;
    background: var(--purple);
    border: 3px solid var(--gold);
    border-radius: var(--radius-lg);
    flex-direction: column;
    align-items: stretch;
    gap: 4px;
    padding: 14px;
    box-shadow: 0 16px 48px rgba(45, 27, 78, 0.4);
    z-index: 1990;
  }

  .site-nav[data-open] {
    display: flex;
  }

  .nav-link {
    color: var(--peach-light);
    background: transparent;
    border: 2px solid transparent;
    border-radius: var(--radius-sm);
    padding: 12px 16px;
    font-size: 1rem;
    text-align: left;
  }

  .nav-link:hover {
    background: var(--purple-black);
    color: var(--gold);
    border-color: rgba(255, 215, 0, 0.5);
  }

  .nav-link[aria-current="page"] {
    background: var(--peach-deep);
    color: var(--gold);
    border-color: var(--gold);
  }

  .page-caption {
    margin-top: var(--space-3);
  }
}

@media (max-width: 640px) {
  .header-shell {
    min-height: 68px;
  }

  .brand-mark {
    width: 40px;
    height: 40px;
  }

  .brand-mark::before {
    width: 14px;
    height: 14px;
    top: 7px;
    left: 11px;
  }

  .brand-name {
    font-size: 1.2rem;
  }

  .brand-badge {
    font-size: 0.6rem;
  }

  .site-nav {
    top: 68px;
  }

  .grid-cards,
  .grid-cards.two-col,
  .grid-cards.four-col {
    grid-template-columns: 1fr;
    gap: var(--space-3);
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: var(--space-4);
  }

  .footer-brand {
    margin-bottom: var(--space-4);
  }

  .footer-legal {
    flex-direction: column;
    gap: 6px;
  }

  .toc-item {
    flex-wrap: wrap;
    gap: var(--space-1) var(--space-2);
  }

  .toc-link-meta {
    margin-left: 0;
  }

  .chapter-title {
    font-size: 1.5rem;
  }

  .back-to-top {
    width: 46px;
    height: 46px;
    right: 16px;
    bottom: 16px;
  }
}

/* ============ Reduced Motion ============ */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }

  .card:hover,
  .toc-item:hover,
  .nav-link:hover,
  .back-to-top:hover {
    transform: none;
  }
}

/* ============ Print ============ */
@media print {
  .site-header,
  .site-footer,
  .back-to-top,
  .scroll-progress {
    display: none !important;
  }

  body {
    background: #fff;
    color: #000;
  }
}