/* ===== RESET ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body { min-height: 100vh; line-height: 1.6; -webkit-font-smoothing: antialiased; }
img, svg { display: block; max-width: 100%; }
ul, ol { list-style: none; }
a { text-decoration: none; color: inherit; }
button { background: none; border: none; cursor: pointer; font: inherit; color: inherit; }
input { font: inherit; border: none; outline: none; background: none; }
:focus-visible { outline: 2px solid #D4A843; outline-offset: 2px; }
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; } }

/* ===== CSS VARIABLES ===== */
:root {
  --primary-dark: #0A1D3F;
  --primary-mid: #1B3A6B;
  --accent-gold: #D4A843;
  --accent-orange: #F26C4F;
  --bg-light: #F5F5F5;
  --bg-white: #FFFFFF;
  --text-primary: #E0E0E0;
  --text-dark: #333333;
  --header-w: 240px;
  --font-heading: 'Oswald', sans-serif;
  --font-body: 'Open Sans', sans-serif;
  --font-accent: 'Playfair Display', serif;
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 40px;
  --grid-col: 12;
  --grid-gap: 20px;
}

/* ===== TYPOGRAPHY ===== */
body { font-family: var(--font-body); font-weight: 400; line-height: 1.8; color: var(--text-dark); background: var(--bg-light); }
h1, h2, h3, h4, h5, h6 { font-family: var(--font-heading); font-weight: 700; letter-spacing: 1px; line-height: 1.1; }
h1 { font-size: clamp(2rem, 5vw, 3.2rem); }
h2 { font-size: clamp(1.5rem, 4vw, 2.4rem); }
h3 { font-size: clamp(1.2rem, 3vw, 1.8rem); }
p { margin-bottom: 1rem; }

/* ===== SKIP LINK ===== */
.skip-link { position: absolute; top: -100%; left: 8px; z-index: 9999; background: var(--accent-gold); color: var(--primary-dark); padding: 8px 16px; font-weight: 700; font-size: 0.875rem; transition: top 0.2s; }
.skip-link:focus { top: 8px; }

/* ===== MOBILE HEADER BAR ===== */
.header-mobile-bar { display: none; position: fixed; top: 0; left: 0; right: 0; z-index: 1001; background: var(--primary-dark); padding: 12px 16px; align-items: center; justify-content: space-between; border-bottom: 1px solid rgba(212, 168, 67, 0.2); }
.header-mobile-logo { font-family: var(--font-heading); font-size: 1.25rem; font-weight: 700; color: var(--accent-gold); letter-spacing: 2px; }
.header-mobile-toggle { display: flex; flex-direction: column; gap: 4px; padding: 4px; }
.toggle-bar { display: block; width: 24px; height: 2px; background: var(--accent-gold); transition: transform 0.3s, opacity 0.3s; }
.header-mobile-toggle[aria-expanded="true"] .toggle-bar:nth-child(1) { transform: translateY(6px) rotate(45deg); }
.header-mobile-toggle[aria-expanded="true"] .toggle-bar:nth-child(2) { opacity: 0; }
.header-mobile-toggle[aria-expanded="true"] .toggle-bar:nth-child(3) { transform: translateY(-6px) rotate(-45deg); }

/* ===== SIDE NAV ===== */
.side-nav { position: fixed; left: 0; top: 0; width: var(--header-w); height: 100vh; background: var(--primary-dark); z-index: 1000; display: flex; flex-direction: column; border-right: 1px solid rgba(212, 168, 67, 0.15); transition: transform 0.35s cubic-bezier(0.25, 0.46, 0.45, 0.94); }
.side-nav-header { padding: 28px 20px 12px; display: flex; align-items: center; justify-content: space-between; position: relative; z-index: 2; }
.side-nav-logo { font-family: var(--font-heading); font-size: 1.4rem; font-weight: 700; color: var(--accent-gold); letter-spacing: 3px; line-height: 1.2; }
.side-nav-logo::after { content: ''; display: block; width: 40px; height: 2px; background: var(--accent-gold); margin-top: 4px; }

/* search toggle */
.search-toggle { padding: 6px; border: 1px solid rgba(212, 168, 67, 0.3); transition: border-color 0.25s; display: flex; align-items: center; justify-content: center; }
.search-toggle:hover { border-color: var(--accent-gold); }
.search-icon { display: block; }

/* search expand */
.search-expand { max-height: 0; overflow: hidden; padding: 0 20px; transition: max-height 0.3s ease, padding 0.3s ease; }
.search-expand[data-active="true"] { max-height: 60px; padding: 8px 20px 12px; }
.search-input { width: 100%; padding: 8px 12px; background: rgba(255,255,255,0.06); border: 1px solid rgba(212, 168, 67, 0.25); color: var(--text-primary); font-size: 0.85rem; font-family: var(--font-body); transition: border-color 0.25s; }
.search-input::placeholder { color: rgba(224,224,224,0.5); }
.search-input:focus { border-color: var(--accent-gold); }

/* track line */
.side-nav-track { position: absolute; left: 60px; top: 80px; bottom: 80px; width: 1px; background: linear-gradient(to bottom, var(--accent-gold), rgba(212, 168, 67, 0.1)); z-index: 0; }

/* nav list */
.side-nav-list { flex: 1; display: flex; flex-direction: column; justify-content: center; padding: 20px 0; position: relative; z-index: 1; }
.side-nav-item { position: relative; }
.side-nav-link { display: flex; align-items: center; gap: 12px; padding: 14px 20px 14px 80px; font-family: var(--font-heading); font-size: 0.9rem; font-weight: 500; letter-spacing: 1px; color: var(--text-primary); transition: background 0.25s, color 0.25s; position: relative; text-transform: uppercase; }
.side-nav-link::before { content: ''; position: absolute; left: 56px; top: 50%; width: 8px; height: 8px; border: 1px solid var(--accent-gold); background: transparent; transform: translateY(-50%) rotate(45deg); transition: background 0.25s, transform 0.25s; }
.side-nav-link:hover { background: rgba(212, 168, 67, 0.08); color: var(--accent-gold); }
.side-nav-link:hover::before { background: var(--accent-gold); transform: translateY(-50%) rotate(45deg) scale(1.2); }
.side-nav-link[aria-current="page"] { background: rgba(212, 168, 67, 0.12); color: var(--accent-gold); border-right: 3px solid var(--accent-gold); }
.side-nav-link[aria-current="page"]::before { background: var(--accent-gold); box-shadow: 0 0 8px rgba(212, 168, 67, 0.5); }
.nav-number { font-family: var(--font-accent); font-size: 0.7rem; font-weight: 400; font-style: italic; color: var(--accent-gold); opacity: 0.7; min-width: 24px; }
.nav-label { font-size: 0.85rem; }

/* side nav footer */
.side-nav-footer { padding: 20px; border-top: 1px solid rgba(212, 168, 67, 0.1); text-align: center; }
.nav-footer-text { font-size: 0.65rem; color: rgba(224,224,224,0.35); letter-spacing: 2px; text-transform: uppercase; }

/* ===== NAV OVERLAY (mobile) ===== */
.nav-overlay { display: none; position: fixed; inset: 0; background: rgba(10, 29, 63, 0.7); z-index: 999; opacity: 0; transition: opacity 0.35s; }
.nav-overlay[data-open="true"] { display: block; opacity: 1; }

/* ===== MAIN CONTENT WRAPPER ===== */
#main-content { margin-left: var(--header-w); min-height: 100vh; }
@media (max-width: 900px) { #main-content { margin-left: 0; padding-top: 60px; } }

/* ===== FRAME VIEWPORT (框景首屏) ===== */
.frame-viewport { position: relative; border: 2px solid var(--accent-gold); padding: 28px; background: var(--bg-white); margin-bottom: var(--space-xl); }
.frame-viewport::before { content: ''; position: absolute; left: -8px; top: -8px; right: -8px; bottom: -8px; border: 1px solid rgba(212, 168, 67, 0.2); pointer-events: none; }
.frame-viewport::after { content: ''; position: absolute; left: 12px; top: 12px; width: 32px; height: 32px; border-left: 1px solid var(--accent-gold); border-top: 1px solid var(--accent-gold); pointer-events: none; }
.frame-viewport .frame-corner { position: absolute; right: 12px; bottom: 12px; width: 32px; height: 32px; border-right: 1px solid var(--accent-gold); border-bottom: 1px solid var(--accent-gold); pointer-events: none; }

/* ===== EXHIBITION TAG ===== */
.section-tag { display: inline-flex; align-items: center; gap: 8px; font-family: var(--font-accent); font-size: 0.8rem; font-style: italic; color: var(--accent-gold); margin-bottom: var(--space-sm); letter-spacing: 1px; }
.section-tag::before { content: attr(data-number); font-family: var(--font-heading); font-size: 1rem; font-weight: 700; font-style: normal; color: var(--primary-dark); background: var(--accent-gold); padding: 2px 8px; }

/* ===== GRID SYSTEM ===== */
.grid { display: grid; grid-template-columns: repeat(var(--grid-col), 1fr); gap: var(--grid-gap); }
@media (max-width: 768px) { .grid { grid-template-columns: repeat(4, 1fr); gap: 12px; } }

/* ===== BUTTONS ===== */
.btn { display: inline-flex; align-items: center; justify-content: center; padding: 10px 24px; font-family: var(--font-heading); font-size: 0.85rem; font-weight: 600; letter-spacing: 1px; text-transform: uppercase; transition: background 0.25s, color 0.25s, border-color 0.25s; border: 1px solid transparent; }
.btn-primary { background: var(--accent-gold); color: var(--primary-dark); border-color: var(--accent-gold); }
.btn-primary:hover { background: transparent; color: var(--accent-gold); }
.btn-outline { background: transparent; color: var(--accent-gold); border-color: var(--accent-gold); }
.btn-outline:hover { background: var(--accent-gold); color: var(--primary-dark); }
.btn-accent { background: var(--accent-orange); color: var(--bg-white); border-color: var(--accent-orange); }
.btn-accent:hover { background: transparent; color: var(--accent-orange); }

/* ===== BREADCRUMB ===== */
.breadcrumb { display: flex; flex-wrap: wrap; gap: 6px; padding: 12px 0; font-size: 0.8rem; color: var(--text-dark); opacity: 0.65; }
.breadcrumb a { color: var(--primary-mid); transition: color 0.2s; }
.breadcrumb a:hover { color: var(--accent-gold); }
.breadcrumb-sep { margin: 0 4px; }

/* ===== CONTAINER ===== */
.container { max-width: 1200px; margin: 0 auto; padding: 0 var(--space-lg); }
@media (max-width: 600px) { .container { padding: 0 var(--space-md); } }

/* ===== CARD ===== */
.card { background: var(--bg-white); border: 1px solid rgba(10, 29, 63, 0.08); padding: var(--space-lg); transition: box-shadow 0.3s, transform 0.3s; }
.card:hover { box-shadow: 0 6px 24px rgba(10, 29, 63, 0.10); transform: translateY(-2px); }
.card-title { font-family: var(--font-heading); font-size: 1.1rem; margin-bottom: var(--space-sm); color: var(--primary-dark); }
.card-text { font-size: 0.9rem; color: var(--text-dark); line-height: 1.7; }

/* ===== IMAGE CONTAINER (placeholder) ===== */
.img-frame { position: relative; overflow: hidden; background: var(--primary-mid); min-height: 180px; display: flex; align-items: center; justify-content: center; }
.img-frame .img-placeholder { width: 100%; height: 100%; object-fit: cover; min-height: 180px; background: linear-gradient(135deg, var(--primary-mid) 0%, var(--primary-dark) 100%); }
.img-frame .img-label { position: absolute; bottom: 0; left: 0; right: 0; padding: 8px 12px; background: rgba(10, 29, 63, 0.75); color: var(--accent-gold); font-size: 0.75rem; font-family: var(--font-heading); letter-spacing: 1px; }

/* ===== PROGRESS BAR ===== */
.progress-container { position: fixed; top: 0; left: 0; right: 0; height: 3px; z-index: 2000; background: rgba(212, 168, 67, 0.12); pointer-events: none; }
.progress-bar { height: 100%; width: 0%; background: var(--accent-gold); transition: width 0.1s linear; }
@media (prefers-reduced-motion: reduce) { .progress-bar { transition: none; } }

/* ===== FOOTER ===== */
.site-footer { background: var(--primary-dark); color: var(--text-primary); margin-left: var(--header-w); padding: var(--space-xl) 0 var(--space-lg); border-top: 1px solid rgba(212, 168, 67, 0.08); }
.footer-inner { max-width: 1200px; margin: 0 auto; padding: 0 var(--space-lg); }
.footer-line { display: flex; flex-wrap: wrap; gap: 8px 16px; padding: 12px 0; border-bottom: 1px solid rgba(212, 168, 67, 0.06); align-items: baseline; }
.footer-line:last-child { border-bottom: none; }
.footer-logo { font-family: var(--font-heading); font-size: 1.6rem; font-weight: 700; color: var(--accent-gold); letter-spacing: 3px; }
.footer-tagline { font-size: 0.85rem; color: rgba(224,224,224,0.5); font-style: italic; }
.footer-link { font-size: 0.85rem; color: var(--text-primary); transition: color 0.2s; letter-spacing: 0.5px; }
.footer-link:hover { color: var(--accent-gold); }
.footer-sep { color: rgba(212, 168, 67, 0.2); font-size: 0.8rem; }
.footer-info { font-size: 0.8rem; color: rgba(224,224,224,0.6); }
.footer-copy { font-size: 0.8rem; color: rgba(224,224,224,0.45); }
.footer-icp { font-size: 0.8rem; color: rgba(224,224,224,0.35); }

@media (max-width: 900px) {
  .site-footer { margin-left: 0; }
  .footer-line { flex-direction: column; gap: 4px; }
}

/* ===== MOBILE NAV STATE ===== */
@media (max-width: 900px) {
  .header-mobile-bar { display: flex; }
  .side-nav { transform: translateX(-100%); }
  .side-nav[data-open="true"] { transform: translateX(0); }
  .nav-overlay[data-open="true"] { display: block; opacity: 1; }
}
@media (min-width: 901px) {
  .side-nav[data-open="true"] { transform: translateX(0); }
  .nav-overlay { display: none !important; }
}

/* ===== RESPONSIVE ===== */
@media (max-width: 600px) {
  :root { --header-w: 0px; }
  .side-nav { width: 100%; max-width: 320px; }
  .search-expand[data-active="true"] { max-height: 60px; padding: 8px 20px 12px; }
}
@media (min-width: 601px) and (max-width: 900px) {
  .side-nav { width: 280px; }
}
@media (min-width: 901px) {
  .side-nav { transform: translateX(0) !important; }
}

/* ===== SECTION SPACING ===== */
.section { padding: var(--space-xl) 0; }
.section-dark { background: var(--primary-dark); color: var(--text-primary); }
.section-light { background: var(--bg-light); }

/* ===== UTILITY ===== */
.text-gold { color: var(--accent-gold); }
.text-orange { color: var(--accent-orange); }
.text-dark { color: var(--text-dark); }
.text-small { font-size: 0.85rem; }
.font-heading { font-family: var(--font-heading); }
.font-accent { font-family: var(--font-accent); font-style: italic; }
.mt-lg { margin-top: var(--space-lg); }
.mb-lg { margin-bottom: var(--space-lg); }