/* ===== RESET & VARIABLES ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body { margin: 0; padding: 0 0 0 var(--nav-width); background: var(--color-bg); color: var(--color-text); font-family: var(--font-body); font-size: var(--font-base); line-height: var(--line-body); min-height: 100vh; }
img, svg { display: block; max-width: 100%; height: auto; }
a { color: inherit; text-decoration: none; }
ul, ol { list-style: none; }
button { font: inherit; cursor: pointer; border: none; background: none; color: inherit; }
:focus-visible { outline: 2px solid var(--color-glow); outline-offset: 2px; border-radius: 2px; }

:root {
  --color-bg: #0A0E27;
  --color-bg-elevated: #12183A;
  --color-accent: #FF6B35;
  --color-accent-dark: #D84315;
  --color-text: #F5F7FA;
  --color-text-muted: #8C9EAB;
  --color-glow: #00BCD4;
  --color-border-start: #B0BEC5;
  --color-border-end: #ECEFF1;
  --nav-width: 80px;
  --header-height-mobile: 60px;
  --font-heading: 'Georgia', 'Times New Roman', serif;
  --font-body: 'Arial', 'Helvetica', sans-serif;
  --font-base: 1rem;
  --line-body: 1.6;
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 2rem;
  --space-xl: 3rem;
  --space-2xl: 4rem;
  --grid-gap: var(--space-lg);
  --transition: 0.3s ease;
  --max-width: 1200px;
}

/* ===== CHINESE TYPOGRAPHY ===== */
body { font-family: var(--font-body); -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale; }
h1, h2, h3, h4, h5, h6 { font-family: var(--font-heading); font-weight: 700; font-style: italic; letter-spacing: 0.08em; line-height: 1.2; color: var(--color-text); }

/* ===== SKIP LINK ===== */
.skip-link { position: fixed; top: -999px; left: var(--space-md); z-index: 10000; padding: var(--space-sm) var(--space-md); background: var(--color-accent); color: #fff; font-weight: 700; font-size: 0.875rem; border-radius: 0 0 4px 4px; }
.skip-link:focus { top: 0; }

/* ===== HEADER (SIDE NAV) ===== */
.site-header { position: fixed; top: 0; left: 0; width: var(--nav-width); height: 100vh; background: var(--color-bg-elevated); border-right: 1px solid; border-image: linear-gradient(180deg, var(--color-border-start), var(--color-border-end)) 1; z-index: 1000; display: flex; flex-direction: column; }
.header-inner { display: flex; flex-direction: column; height: 100%; padding: var(--space-lg) 0; align-items: center; }
.brand { display: flex; flex-direction: column; align-items: center; gap: var(--space-xs); padding: 0 var(--space-sm); margin-bottom: var(--space-xl); }
.brand-icon { width: 28px; height: 28px; }
.brand-name { font-family: var(--font-heading); font-size: 0.75rem; font-weight: 700; letter-spacing: 0.12em; color: var(--color-text); text-align: center; line-height: 1.3; text-transform: uppercase; }

.nav-toggle { display: none; }

.nav-backdrop { display: none; }

.nav-container { flex: 1; display: flex; flex-direction: column; width: 100%; }
.nav-list { display: flex; flex-direction: column; align-items: center; gap: var(--space-sm); padding: 0 var(--space-sm); width: 100%; }
.nav-list li { width: 100%; }
.nav-list a { display: block; width: 100%; padding: var(--space-sm) 0; text-align: center; font-size: 0.7rem; font-weight: 400; color: var(--color-text-muted); letter-spacing: 0.04em; border-left: 2px solid transparent; transition: color var(--transition), border-color var(--transition); word-break: keep-all; }
.nav-list a:hover, .nav-list a:focus-visible { color: var(--color-glow); border-left-color: var(--color-glow); }
.nav-list a[aria-current="page"] { color: var(--color-text); border-left-color: var(--color-accent); font-weight: 600; }

.nav-cta { display: block; margin: var(--space-lg) var(--space-sm) 0; padding: var(--space-sm) var(--space-xs); background: var(--color-accent); color: #fff; font-size: 0.65rem; font-weight: 700; letter-spacing: 0.06em; text-align: center; border-radius: 0; transition: background var(--transition), transform var(--transition); text-transform: uppercase; }
.nav-cta:hover { background: var(--color-accent-dark); transform: scale(1.04); }
.nav-cta:active { transform: scale(0.96); }

/* ===== FOOTER ===== */
.site-footer { background: var(--color-bg); border-top: 1px solid; border-image: linear-gradient(90deg, var(--color-border-start), var(--color-border-end)) 1; padding: var(--space-xl) var(--space-lg); margin-top: var(--space-2xl); }
.footer-inner { max-width: var(--max-width); margin: 0 auto; display: flex; flex-wrap: wrap; justify-content: space-between; align-items: center; gap: var(--space-md); }
.footer-col { display: flex; flex-direction: column; gap: var(--space-xs); }
.footer-brand-name { font-family: var(--font-heading); font-size: 1.1rem; font-weight: 700; letter-spacing: 0.1em; color: var(--color-text); }
.footer-tagline { font-size: 0.75rem; color: var(--color-text-muted); max-width: 280px; line-height: 1.5; }
.footer-col-links { flex-direction: row; flex-wrap: wrap; gap: var(--space-md); }
.footer-col-links a { font-size: 0.8rem; color: var(--color-text-muted); transition: color var(--transition); }
.footer-col-links a:hover { color: var(--color-glow); }
.footer-col-contact { font-size: 0.8rem; color: var(--color-text-muted); }
.footer-col-contact a { color: var(--color-text-muted); transition: color var(--transition); }
.footer-col-contact a:hover { color: var(--color-glow); }
.footer-col-copy { font-size: 0.75rem; color: var(--color-text-muted); width: 100%; text-align: center; margin-top: var(--space-md); padding-top: var(--space-md); border-top: 1px solid rgba(140,158,171,0.15); }

/* ===== BASE BUTTON ===== */
.btn { display: inline-flex; align-items: center; justify-content: center; padding: 0.6rem 1.4rem; background: var(--color-accent); color: #fff; font-family: var(--font-body); font-size: 0.9rem; font-weight: 600; letter-spacing: 0.04em; border: none; border-radius: 0; cursor: pointer; transition: background var(--transition), transform var(--transition); text-align: center; }
.btn:hover { background: var(--color-accent-dark); transform: scale(1.02); }
.btn:active { transform: scale(0.97); }
.btn:focus-visible { outline: 2px solid var(--color-glow); outline-offset: 2px; }

/* ===== DECORATIVE ===== */
.deco-line { height: 1px; background: linear-gradient(90deg, var(--color-border-start), var(--color-border-end), transparent); border: none; margin: var(--space-lg) 0; }
.deco-border { border: 1px solid; border-image: linear-gradient(135deg, var(--color-border-start), var(--color-border-end)) 1; }

/* ===== GRID ===== */
.grid { display: grid; gap: var(--grid-gap); grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); }

/* ===== BREADCRUMB ===== */
.breadcrumb { display: flex; flex-wrap: wrap; align-items: center; gap: var(--space-sm); font-size: 0.8rem; color: var(--color-text-muted); margin-bottom: var(--space-lg); }
.breadcrumb a { color: var(--color-text-muted); transition: color var(--transition); }
.breadcrumb a:hover { color: var(--color-glow); }
.breadcrumb span { color: var(--color-text); }
.breadcrumb li + li::before { content: "/"; margin-right: var(--space-sm); color: var(--color-text-muted); }

/* ===== CONTENT CONTAINER ===== */
.content-container { max-width: var(--max-width); margin: 0 auto; padding: 0 var(--space-lg); width: 100%; }

/* ===== SCROLL TOP ===== */
[data-scroll-top] { position: fixed; bottom: var(--space-lg); right: var(--space-lg); z-index: 900; width: 44px; height: 44px; background: var(--color-bg-elevated); border: 1px solid rgba(140,158,171,0.3); color: var(--color-text-muted); font-size: 1.2rem; display: flex; align-items: center; justify-content: center; cursor: pointer; opacity: 0; visibility: hidden; transform: translateY(12px); transition: opacity var(--transition), transform var(--transition), visibility var(--transition), background var(--transition); border-radius: 0; }
[data-scroll-top]:hover { background: var(--color-accent); color: #fff; border-color: var(--color-accent); }
[data-scroll-top][data-visible] { opacity: 1; visibility: visible; transform: translateY(0); }
[data-scroll-top]:focus-visible { outline: 2px solid var(--color-glow); outline-offset: 2px; }

/* ===== RESPONSIVE ===== */
@media (max-width: 1023px) {
  .footer-inner { flex-direction: column; align-items: flex-start; gap: var(--space-md); }
  .footer-col-copy { text-align: left; }
}

@media (max-width: 767px) {
  body { padding: var(--header-height-mobile) 0 0 0; }

  .site-header { width: 100%; height: var(--header-height-mobile); border-right: none; border-bottom: 1px solid; border-image: linear-gradient(90deg, var(--color-border-start), var(--color-border-end)) 1; flex-direction: row; }
  .header-inner { flex-direction: row; padding: 0 var(--space-md); align-items: center; height: 100%; width: 100%; }
  .brand { flex-direction: row; margin-bottom: 0; gap: var(--space-sm); padding: 0; }
  .brand-icon { width: 24px; height: 24px; }
  .brand-name { font-size: 0.85rem; }

  .nav-toggle { display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 4px; margin-left: auto; padding: var(--space-sm); background: none; border: none; cursor: pointer; color: var(--color-text); }
  .nav-toggle-icon { display: block; width: 22px; height: 2px; background: var(--color-text); transition: background var(--transition); border-radius: 0; }
  .nav-toggle-icon::before, .nav-toggle-icon::after { content: ""; display: block; width: 22px; height: 2px; background: var(--color-text); transition: transform var(--transition); border-radius: 0; }
  .nav-toggle-icon::before { transform: translateY(-6px); }
  .nav-toggle-icon::after { transform: translateY(4px); }
  .nav-toggle[aria-expanded="true"] .nav-toggle-icon { background: transparent; }
  .nav-toggle[aria-expanded="true"] .nav-toggle-icon::before { transform: translateY(-2px) rotate(45deg); }
  .nav-toggle[aria-expanded="true"] .nav-toggle-icon::after { transform: translateY(-2px) rotate(-45deg); }
  .nav-toggle-label { font-size: 0.6rem; letter-spacing: 0.06em; color: var(--color-text-muted); }

  .nav-backdrop { display: block; position: fixed; top: var(--header-height-mobile); left: 0; width: 100%; height: 0; background: rgba(10,14,39,0.7); z-index: 998; transition: height 0s var(--transition); }
  [data-nav][data-open] ~ .nav-backdrop { height: 100vh; transition: height 0s 0s; }

  .nav-container { position: fixed; top: var(--header-height-mobile); left: 0; width: 100%; max-height: 0; overflow: hidden; background: var(--color-bg-elevated); border-bottom: 1px solid rgba(140,158,171,0.15); z-index: 999; transition: max-height 0.4s ease, padding 0.3s ease; flex-direction: column; padding: 0 var(--space-md); }
  .nav-container[data-open] { max-height: 80vh; overflow-y: auto; padding: var(--space-md); }
  .nav-list { flex-direction: column; align-items: stretch; gap: var(--space-xs); padding: 0; }
  .nav-list a { text-align: left; padding: var(--space-sm) var(--space-sm); font-size: 0.9rem; border-left: none; border-bottom: 1px solid rgba(140,158,171,0.08); }
  .nav-list a[aria-current="page"] { border-left: none; border-bottom-color: var(--color-accent); color: var(--color-accent); }
  .nav-list a:hover { border-left: none; color: var(--color-glow); }
  .nav-cta { margin: var(--space-md) 0 0; font-size: 0.8rem; padding: var(--space-sm) var(--space-md); }

  .site-footer { padding: var(--space-lg) var(--space-md); margin-top: var(--space-xl); }
  .footer-inner { flex-direction: column; align-items: flex-start; }
  .footer-col-links { flex-direction: column; gap: var(--space-sm); }
  .footer-col-copy { text-align: left; }
}

/* ===== PREFERS REDUCED MOTION ===== */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; scroll-behavior: auto !important; }
  html { scroll-behavior: auto; }
  .nav-cta:hover { transform: none; }
  .btn:hover { transform: none; }
  [data-scroll-top] { transition: none; }
  .nav-container { transition: none; }
  .nav-toggle-icon, .nav-toggle-icon::before, .nav-toggle-icon::after { transition: none; }
}