/* ============ RESET & VARIABLES ============ */
*,
*::before,
*::after {
  box-sizing: border-box;
}

:root {
  --color-deep-blue: #0B1B3D;
  --color-passion-red: #E63946;
  --color-gold: #F4A261;
  --color-glass: rgba(255, 255, 255, 0.08);
  --color-white: #FFFFFF;
  --color-light-blue: #B0C4DE;
  --color-cyan: #00E5FF;
  --color-dark-base: #071228;
  --font-headline: 'Noto Serif SC', 'Source Han Serif SC', 'Songti SC', serif;
  --font-body: 'Microsoft YaHei', 'PingFang SC', 'Helvetica Neue', sans-serif;
  --font-number: 'Roboto Mono', 'DIN Alternate', 'SFMono-Regular', Consolas, monospace;
  --container-max: 1280px;
  --header-height: 72px;
  --radius: 12px;
  --space: 16px;
}

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

body {
  margin: 0;
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-white);
  background:
    radial-gradient(ellipse at 85% -10%, rgba(230, 57, 70, 0.16) 0%, transparent 55%),
    radial-gradient(ellipse at 12% 28%, rgba(0, 229, 255, 0.06) 0%, transparent 45%),
    linear-gradient(180deg, var(--color-deep-blue) 0%, var(--color-dark-base) 100%);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4, h5, h6 {
  margin: 0 0 0.5em;
  font-weight: 700;
  line-height: 1.25;
  color: var(--color-white);
}

p {
  margin: 0 0 1em;
}

ul, ol {
  margin: 0 0 1em;
  padding-left: 1.25em;
}

a {
  color: var(--color-cyan);
  transition: color 0.25s;
}

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

button,
input,
select,
textarea {
  font: inherit;
}

:focus-visible {
  outline: 3px solid var(--color-cyan);
  outline-offset: 3px;
  border-radius: 2px;
}

/* ============ CONTAINER & MAIN ============ */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: 32px;
}

.main-content {
  display: block;
  min-height: 60vh;
}

/* ============ SKIP LINK ============ */
.skip-link {
  position: absolute;
  top: -48px;
  left: 16px;
  z-index: 200;
  display: inline-block;
  padding: 10px 20px;
  background: var(--color-passion-red);
  color: var(--color-white);
  font-size: 14px;
  font-weight: 600;
  text-decoration: none;
  border-radius: 0 0 6px 6px;
  transition: top 0.2s ease;
}

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

/* ============ HEADER ============ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(7, 18, 40, 0.92);
  -webkit-backdrop-filter: blur(14px);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.site-header::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--color-passion-red) 0%, var(--color-gold) 100%);
  pointer-events: none;
  z-index: 3;
}

.site-header__progress {
  position: absolute;
  bottom: -1px;
  left: 0;
  height: 2px;
  width: 0%;
  background: var(--color-cyan);
  box-shadow: 0 0 10px rgba(0, 229, 255, 0.6);
  z-index: 2;
  pointer-events: none;
}

.site-header__inner {
  position: relative;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  min-height: var(--header-height);
}

.site-header__inner::before,
.site-header__inner::after {
  content: "";
  position: absolute;
  width: 16px;
  height: 16px;
  border: 1px solid rgba(255, 255, 255, 0.16);
  pointer-events: none;
}

.site-header__inner::before {
  top: 6px;
  left: 0;
  border-right: 0;
  border-bottom: 0;
}

.site-header__inner::after {
  bottom: 6px;
  right: 0;
  border-left: 0;
  border-top: 0;
}

/* Brand */
.site-header__brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  flex-shrink: 0;
  text-decoration: none;
}

.site-header__brand-mark {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border: 2px solid var(--color-passion-red);
  border-radius: 10px;
  background: rgba(230, 57, 70, 0.12);
  font-family: var(--font-number);
  font-size: 18px;
  font-weight: 700;
  color: var(--color-white);
}

.site-header__brand-mark::after {
  content: "";
  position: absolute;
  right: 3px;
  bottom: 3px;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-cyan);
  box-shadow: 0 0 8px var(--color-cyan);
}

.site-header__brand-text {
  display: inline-flex;
  flex-direction: column;
  line-height: 1.2;
}

.site-header__brand-cn {
  font-family: var(--font-headline);
  font-size: 20px;
  font-weight: 700;
  letter-spacing: 2px;
  color: var(--color-white);
}

.site-header__brand-en {
  font-family: var(--font-number);
  font-size: 10px;
  letter-spacing: 3px;
  color: var(--color-gold);
  text-transform: uppercase;
}

/* Primary nav */
.site-nav {
  flex: 1;
  display: flex;
  justify-content: center;
}

.site-nav__list {
  display: flex;
  align-items: center;
  gap: 2px;
  margin: 0;
  padding: 0;
  list-style: none;
  counter-reset: navIndex;
}

.site-nav__item {
  counter-increment: navIndex;
  position: relative;
}

.site-nav__link {
  position: relative;
  display: inline-flex;
  align-items: baseline;
  gap: 6px;
  padding: 10px 12px;
  color: var(--color-light-blue);
  font-size: 15px;
  text-decoration: none;
  white-space: nowrap;
  transition: color 0.25s;
}

.site-nav__link::before {
  content: "0" counter(navIndex);
  font-family: var(--font-number);
  font-size: 10px;
  letter-spacing: 1px;
  color: var(--color-gold);
  opacity: 0.7;
}

.site-nav__link::after {
  content: "";
  position: absolute;
  left: 12px;
  right: 12px;
  bottom: 4px;
  height: 2px;
  background: var(--color-passion-red);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.3s;
}

.site-nav__link:hover,
.site-nav__link:focus-visible {
  color: var(--color-white);
}

.site-nav__link:hover::after,
.site-nav__link:focus-visible::after {
  transform: scaleX(1);
}

.site-nav__link[aria-current="page"] {
  color: var(--color-white);
  font-weight: 600;
}

.site-nav__link[aria-current="page"]::before {
  color: var(--color-passion-red);
  opacity: 1;
}

.site-nav__link[aria-current="page"]::after {
  transform: scaleX(1);
}

/* Header actions */
.site-header__actions {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-shrink: 0;
}

.site-header__lang {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 7px 12px;
  font-size: 13px;
  color: var(--color-light-blue);
  text-decoration: none;
  border: 1px solid rgba(255, 255, 255, 0.18);
  border-radius: 6px;
  transition: border-color 0.25s, color 0.25s;
}

.site-header__lang::before {
  content: "中";
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 18px;
  height: 18px;
  font-size: 12px;
  line-height: 1;
  color: var(--color-gold);
  border: 1px solid var(--color-gold);
  border-radius: 3px;
}

.site-header__lang:hover,
.site-header__lang:focus-visible {
  border-color: var(--color-gold);
  color: var(--color-white);
}

/* Toggle */
.site-header__toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  padding: 0;
  background: transparent;
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: 8px;
  cursor: pointer;
  transition: border-color 0.25s;
}

.site-header__toggle:hover,
.site-header__toggle:focus-visible {
  border-color: var(--color-gold);
}

.site-header__toggle-box {
  display: block;
  width: 20px;
}

.site-header__toggle-bar {
  display: block;
  width: 20px;
  height: 2px;
  margin: 4px 0;
  background: var(--color-white);
  border-radius: 2px;
  transition: transform 0.25s, opacity 0.25s;
}

.site-header__toggle[aria-expanded="true"] .site-header__toggle-bar:nth-child(1) {
  transform: translateY(6px) rotate(45deg);
}

.site-header__toggle[aria-expanded="true"] .site-header__toggle-bar:nth-child(2) {
  opacity: 0;
}

.site-header__toggle[aria-expanded="true"] .site-header__toggle-bar:nth-child(3) {
  transform: translateY(-6px) rotate(-45deg);
}

/* ============ BUTTONS ============ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 22px;
  border: 1px solid transparent;
  border-radius: 6px;
  font-family: var(--font-body);
  font-size: 15px;
  font-weight: 500;
  line-height: 1;
  color: var(--color-white);
  text-decoration: none;
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s, background-color 0.2s, border-color 0.2s;
}

.btn--primary {
  background: linear-gradient(135deg, var(--color-passion-red) 0%, #b3222e 100%);
  box-shadow: 0 4px 18px rgba(230, 57, 70, 0.35);
}

.btn--primary:hover,
.btn--primary:focus-visible {
  transform: translateY(-2px);
  box-shadow: 0 8px 28px rgba(230, 57, 70, 0.5);
}

.btn--small {
  padding: 10px 16px;
  font-size: 14px;
}

.btn--install::before {
  content: "↓";
  font-family: var(--font-number);
  font-size: 16px;
  font-weight: 700;
  line-height: 1;
}

/* ============ FOOTER ============ */
.site-footer {
  position: relative;
  margin-top: 80px;
  background: var(--color-dark-base);
}

.site-footer::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--color-passion-red) 0%, var(--color-gold) 60%, var(--color-cyan) 100%);
  pointer-events: none;
}

.site-footer__top {
  padding: 56px 0 40px;
}

.site-footer__grid {
  display: grid;
  grid-template-columns: 2.2fr 1fr 1fr 1.4fr;
  gap: 40px;
}

.site-footer__brand-block {
  max-width: 340px;
}

.site-footer__logo {
  display: inline-block;
  position: relative;
  margin-bottom: 16px;
  padding-bottom: 8px;
  font-family: var(--font-headline);
  font-size: 24px;
  font-weight: 700;
  letter-spacing: 2px;
  color: var(--color-white);
  text-decoration: none;
}

.site-footer__logo::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0;
  width: 32px;
  height: 3px;
  background: var(--color-passion-red);
}

.site-footer__desc {
  margin-bottom: 16px;
  font-size: 15px;
  line-height: 1.7;
  color: var(--color-light-blue);
}

.site-footer__trust {
  margin: 0;
  padding-left: 12px;
  border-left: 2px solid var(--color-gold);
  font-size: 13px;
  line-height: 1.6;
  color: rgba(176, 196, 222, 0.7);
}

.site-footer__col {
  min-width: 0;
}

.site-footer__heading {
  margin-bottom: 20px;
  font-family: var(--font-headline);
  font-size: 16px;
  font-weight: 700;
  letter-spacing: 1px;
  color: var(--color-white);
}

.site-footer__heading::after {
  content: "";
  display: block;
  width: 24px;
  height: 2px;
  margin-top: 8px;
  background: var(--color-passion-red);
}

.site-footer__list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.site-footer__list li {
  margin-bottom: 4px;
}

.site-footer__list a {
  display: inline-block;
  padding: 4px 0;
  color: var(--color-light-blue);
  font-size: 14px;
  text-decoration: none;
  transition: color 0.25s, transform 0.25s;
}

.site-footer__list a::before {
  content: "›";
  margin-right: 6px;
  font-family: var(--font-number);
  font-weight: 700;
  color: var(--color-gold);
}

.site-footer__list a:hover,
.site-footer__list a:focus-visible {
  color: var(--color-white);
  transform: translateX(3px);
}

.site-footer__contact-list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.site-footer__contact-item {
  position: relative;
  margin-bottom: 12px;
  padding-left: 18px;
  color: var(--color-light-blue);
  font-size: 14px;
  line-height: 1.6;
  word-break: break-all;
}

.site-footer__contact-item::before {
  content: "";
  position: absolute;
  left: 0;
  top: 10px;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-passion-red);
}

.site-footer__contact-label {
  display: block;
  margin-bottom: 2px;
  font-family: var(--font-number);
  font-size: 11px;
  letter-spacing: 2px;
  color: var(--color-gold);
}

.site-footer__note {
  margin: 12px 0 0;
  padding: 8px 12px;
  border-radius: 6px;
  background: rgba(255, 255, 255, 0.04);
  font-size: 12px;
  line-height: 1.5;
  color: rgba(176, 196, 222, 0.6);
}

.site-footer__bottom {
  padding: 20px 0;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  background: rgba(0, 0, 0, 0.15);
}

.site-footer__bottom-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px 16px;
}

.site-footer__copyright,
.site-footer__icp {
  margin: 0;
  font-size: 13px;
  color: rgba(255, 255, 255, 0.5);
}

/* ============ BACK TO TOP ============ */
.back-top {
  position: fixed;
  right: 24px;
  bottom: 24px;
  z-index: 90;
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  width: 52px;
  height: 52px;
  padding: 0;
  background: rgba(7, 18, 40, 0.9);
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: 50%;
  color: var(--color-white);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: opacity 0.3s, transform 0.3s, visibility 0.3s, border-color 0.3s;
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
}

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

.back-top:hover,
.back-top:focus-visible {
  border-color: var(--color-gold);
}

.back-top__icon {
  font-family: var(--font-number);
  font-size: 16px;
  font-weight: 700;
  line-height: 1;
  color: var(--color-gold);
}

/* ============ BREADCRUMB ============ */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
  margin: 0 0 24px;
  padding: 0;
  list-style: none;
  font-size: 14px;
}

.breadcrumb__item {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--color-light-blue);
}

.breadcrumb__item:not(:last-child)::after {
  content: "/";
  font-family: var(--font-number);
  color: rgba(255, 255, 255, 0.3);
}

.breadcrumb__link {
  color: var(--color-light-blue);
  text-decoration: none;
}

.breadcrumb__link:hover,
.breadcrumb__link:focus-visible {
  color: var(--color-white);
}

.breadcrumb__item[aria-current="page"] {
  color: var(--color-white);
}

/* ============ PAGE HEADINGS ============ */
.page-title {
  margin-bottom: 16px;
  font-family: var(--font-headline);
  font-size: 40px;
  font-weight: 700;
  line-height: 1.3;
  color: var(--color-white);
}

.page-lead {
  max-width: 720px;
  margin-bottom: 24px;
  font-size: 18px;
  line-height: 1.7;
  color: var(--color-light-blue);
}

/* ============ CHAPTER SECTION ============ */
.chapter-section {
  position: relative;
  padding: 64px 0;
  scroll-margin-top: 88px;
}

.chapter-section--rule {
  border-top: 1px solid rgba(255, 255, 255, 0.08);
}

.chapter-section__header {
  display: flex;
  align-items: flex-start;
  gap: 20px;
  margin-bottom: 36px;
}

.chapter-section__index {
  flex-shrink: 0;
  min-width: 68px;
  font-family: var(--font-number);
  font-size: 56px;
  font-weight: 700;
  line-height: 1;
  color: var(--color-passion-red);
  opacity: 0.35;
}

.chapter-section__title {
  margin-bottom: 6px;
  font-family: var(--font-headline);
  font-size: 32px;
  color: var(--color-white);
}

.chapter-section__lead {
  max-width: 640px;
  margin: 0;
  font-size: 16px;
  line-height: 1.7;
  color: var(--color-light-blue);
}

.chapter-section__body {
  position: relative;
}

/* ============ SECTION LABEL ============ */
.section-label {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-number);
  font-size: 13px;
  letter-spacing: 2px;
  color: var(--color-gold);
  text-transform: uppercase;
}

.section-label::before {
  content: "";
  width: 22px;
  height: 2px;
  background: var(--color-gold);
}

/* ============ GLASS CARD ============ */
.glass-card {
  padding: 24px;
  border-radius: var(--radius);
  background: var(--color-glass);
  border: 1px solid rgba(255, 255, 255, 0.1);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  transition: transform 0.3s, border-color 0.3s, background-color 0.3s;
}

.glass-card:hover {
  transform: translateY(-4px);
  border-color: rgba(0, 229, 255, 0.35);
  background: rgba(255, 255, 255, 0.12);
}

/* ============ TAG ============ */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 10px;
  border: 1px solid rgba(244, 162, 97, 0.35);
  border-radius: 4px;
  background: rgba(244, 162, 97, 0.12);
  font-family: var(--font-number);
  font-size: 12px;
  letter-spacing: 1px;
  color: var(--color-gold);
}

/* ============ DATA STAT ============ */
.data-stat {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.data-stat__value {
  font-family: var(--font-number);
  font-size: 40px;
  font-weight: 700;
  line-height: 1.2;
  color: var(--color-cyan);
}

.data-stat__label {
  font-size: 14px;
  color: var(--color-light-blue);
}

/* ============ STATUS PANEL ============ */
.status-panel {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin-top: 16px;
  padding: 10px 16px;
  border: 1px solid rgba(255, 255, 255, 0.12);
  border-radius: 8px;
  background: rgba(7, 18, 40, 0.7);
  font-size: 13px;
  color: var(--color-light-blue);
}

.status-panel__dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--color-cyan);
  box-shadow: 0 0 8px var(--color-cyan);
  animation: statusPulse 2s infinite ease-in-out;
}

@keyframes statusPulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.4; }
}

/* ============ MEDIA FRAME ============ */
.media-frame {
  position: relative;
  overflow: hidden;
  min-height: 120px;
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius);
  background: linear-gradient(135deg, var(--color-deep-blue), var(--color-dark-base));
}

.media-frame::before {
  content: "";
  display: block;
  padding-top: 62.5%;
}

.media-frame--wide::before { padding-top: 42.857%; }
.media-frame--square::before { padding-top: 100%; }
.media-frame--tall::before { padding-top: 130%; }
.media-frame--portrait::before { padding-top: 125%; }

.media-frame > img,
.media-frame > video,
.media-frame__media {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.media-frame--placeholder::after {
  content: attr(data-placeholder);
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-number);
  font-size: 13px;
  letter-spacing: 3px;
  color: var(--color-light-blue);
  opacity: 0.6;
}

.media-frame__caption {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  padding: 32px 16px 12px;
  background: linear-gradient(transparent, rgba(7, 18, 40, 0.7));
  font-size: 13px;
  color: rgba(255, 255, 255, 0.85);
}

/* ============ GRID ============ */
.grid {
  display: grid;
  gap: 24px;
}

.grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid--4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.grid--2-1 { grid-template-columns: minmax(0, 2fr) minmax(0, 1fr); }
.grid--1-2 { grid-template-columns: minmax(0, 1fr) minmax(0, 2fr); }

/* ============ UTILITIES ============ */
.screen-reader-text {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.text-gradient {
  background: linear-gradient(120deg, var(--color-gold), var(--color-passion-red));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
}

/* ============ REVEAL ============ */
.js-enabled [data-reveal] {
  opacity: 0;
  transform: translateY(28px);
  transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.js-enabled [data-reveal].is-revealed {
  opacity: 1;
  transform: translateY(0);
}

/* ============ NO-JS FALLBACK ============ */
.no-js .site-header__toggle {
  display: none !important;
}

.no-js .site-nav {
  position: static !important;
  display: flex !important;
  flex: 1 1 100%;
  justify-content: center;
  opacity: 1 !important;
  visibility: visible !important;
  transform: none !important;
}

.no-js .site-nav__list {
  flex-wrap: wrap;
  justify-content: center;
}

.no-js .site-header__inner::before,
.no-js .site-header__inner::after {
  display: none;
}

/* ============ RESPONSIVE ============ */
@media (max-width: 1080px) {
  .site-header__lang {
    display: none;
  }

  .site-footer__grid {
    grid-template-columns: 1.5fr 1fr 1fr;
  }

  .site-footer__brand-block {
    grid-column: 1 / -1;
    max-width: none;
  }
}

@media (max-width: 960px) {
  :root {
    --header-height: 60px;
  }

  .site-header__inner::before,
  .site-header__inner::after {
    display: none;
  }

  .site-header__toggle {
    display: inline-flex;
  }

  .site-nav {
    flex: 1 1 100%;
    order: 5;
    display: flex;
    justify-content: center;
    padding: 8px 0 16px;
  }

  .site-nav__list {
    flex-wrap: wrap;
    justify-content: center;
    gap: 4px 8px;
  }

  .js-enabled .site-header__toggle {
    display: inline-flex;
  }

  .js-enabled .site-nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex: none;
    order: 0;
    display: block;
    padding: 0;
    background: var(--color-dark-base);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    box-shadow: 0 16px 32px rgba(0, 0, 0, 0.4);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: opacity 0.25s, transform 0.25s, visibility 0.25s;
  }

  .js-enabled .site-nav[data-open] {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
  }

  .js-enabled .site-nav__list {
    flex-direction: column;
    flex-wrap: nowrap;
    align-items: stretch;
    gap: 0;
    padding: 12px 24px 20px;
  }

  .js-enabled .site-nav__item {
    width: 100%;
  }

  .js-enabled .site-nav__item + .site-nav__item {
    border-top: 1px solid rgba(255, 255, 255, 0.06);
  }

  .js-enabled .site-nav__link {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 14px 4px;
    font-size: 16px;
  }

  .js-enabled .site-nav__link::after {
    display: none;
  }

  .btn--install {
    padding: 10px 14px;
  }
}

@media (max-width: 768px) {
  .container {
    padding-inline: 20px;
  }

  .site-header__actions {
    gap: 8px;
  }

  .btn--install {
    padding: 9px 12px;
    font-size: 13px;
  }

  .site-footer__grid {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }

  .site-footer__brand-block {
    grid-column: 1 / -1;
  }

  .site-footer__top {
    padding: 40px 0 32px;
  }

  .page-title {
    font-size: 32px;
  }

  .chapter-section {
    padding: 48px 0;
  }

  .chapter-section__index {
    font-size: 44px;
    min-width: 52px;
  }

  .chapter-section__title {
    font-size: 26px;
  }

  .grid--4 {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .grid--2,
  .grid--3 {
    grid-template-columns: minmax(0, 1fr);
  }

  .grid--2-1,
  .grid--1-2 {
    grid-template-columns: minmax(0, 1fr);
  }
}

@media (max-width: 480px) {
  .btn--install {
    width: 42px;
    height: 42px;
    padding: 0;
    font-size: 0;
  }

  .btn--install::before {
    font-size: 18px;
  }

  .site-footer__grid {
    grid-template-columns: minmax(0, 1fr);
    gap: 28px;
  }

  .back-top {
    right: 16px;
    bottom: 16px;
    width: 48px;
    height: 48px;
  }

  .data-stat__value {
    font-size: 32px;
  }
}

/* ============ REDUCED MOTION ============ */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }

  .js-enabled [data-reveal] {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .status-panel__dot {
    animation: none;
  }
}