/* ============================================================
   Arcaea Story Archive — Apple-inspired Design v2
   ============================================================ */

:root {
  --bg-primary: #f5f5f7;
  --bg-secondary: #ffffff;
  --bg-sidebar: #1d1d1f;
  --bg-sidebar-hover: #2a2a2d;
  --bg-sidebar-active: #3a3a3e;

  --text-primary: #1d1d1f;
  --text-secondary: #6e6e73;
  --text-tertiary: #aeaeb2;
  --text-sidebar: #c8c8cc;
  --text-sidebar-dim: #86868b;
  --text-sidebar-active: #ffffff;

  --accent: #9b59b6;
  --accent-light: #c39bd3;
  --accent-dark: #7d3c98;

  --border-light: rgba(0,0,0,0.08);
  --border-sidebar: rgba(255,255,255,0.08);

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 20px;

  --sidebar-width: 280px;
  --topbar-height: 48px;

  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text", "Helvetica Neue", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: "SF Mono", "Menlo", "Consolas", monospace;

  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s ease;
  --transition-slow: 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  font-family: var(--font-sans); font-size: 16px;
  -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale;
}

body {
  background: var(--bg-primary); color: var(--text-primary);
  min-height: 100vh; display: flex; overflow-x: hidden;
}

/* ---------- Language visibility ---------- */
.lang-text { display: none; }
html[lang="en"] .lang-en { display: inline; }
html[lang="zh"] .lang-zh { display: inline; }
html[lang="en"] .lang-en.block, html[lang="zh"] .lang-zh.block,
html[lang="en"] p .lang-en, html[lang="zh"] p .lang-zh,
html[lang="en"] .guide-item .lang-en, html[lang="zh"] .guide-item .lang-zh { display: block; }
html[lang="en"] .eqn-label.lang-en, html[lang="zh"] .eqn-label.lang-zh { display: inline; }

/* ---------- Loading Screen ---------- */
#loading-screen {
  position: fixed; inset: 0; z-index: 9999;
  background: var(--bg-primary); display: flex; flex-direction: column;
  align-items: center; justify-content: center; gap: 20px;
  transition: opacity 0.4s ease, visibility 0.4s ease;
}
#loading-screen.hidden { opacity: 0; visibility: hidden; pointer-events: none; }
.loading-icon { color: var(--accent); animation: pulse-icon 2s ease-in-out infinite; }
@keyframes pulse-icon {
  0%, 100% { opacity: 0.6; transform: scale(1); }
  50% { opacity: 1; transform: scale(1.05); }
}
#loading-text { font-size: 14px; color: var(--text-secondary); letter-spacing: 0.5px; }

/* ---------- Top Bar ---------- */
#topbar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  height: var(--topbar-height);
  background: rgba(255,255,255,0.72);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--border-light);
  display: flex; align-items: center; padding: 0 16px; gap: 12px;
}
.icon-btn {
  display: flex; align-items: center; justify-content: center;
  width: 34px; height: 34px; border: none; border-radius: var(--radius-sm);
  background: transparent; color: var(--text-primary); cursor: pointer;
  transition: background var(--transition-fast);
}
.icon-btn:hover { background: rgba(0,0,0,0.06); }
.topbar-title { flex: 1; display: flex; align-items: center; gap: 8px; font-size: 14px; font-weight: 500; overflow: hidden; white-space: nowrap; }
.topbar-act { color: var(--text-secondary); }
.topbar-sep { color: var(--text-tertiary); }
.topbar-sep::before { content: '/'; }
.topbar-sep.hidden { display: none; }
.topbar-story { color: var(--text-primary); }
.topbar-actions { display: flex; align-items: center; gap: 8px; }
.lang-btn {
  display: flex; align-items: center; gap: 6px;
  padding: 5px 10px; border: 1px solid var(--border-light); border-radius: 20px;
  background: var(--bg-secondary); font-size: 12px; font-weight: 500; cursor: pointer;
  transition: all var(--transition-fast);
}
.lang-btn:hover { border-color: var(--accent); }
.lang-option { padding: 2px 6px; border-radius: 12px; transition: all var(--transition-fast); color: var(--text-tertiary); }
.lang-option.active { background: var(--accent); color: #fff; }
.lang-divider { width: 1px; height: 14px; background: var(--border-light); }

/* ---------- Sidebar ---------- */
#sidebar {
  position: fixed; top: 0; left: 0; bottom: 0; width: var(--sidebar-width);
  background: var(--bg-sidebar); color: var(--text-sidebar); z-index: 200;
  display: flex; flex-direction: column; transform: translateX(0);
  transition: transform var(--transition-slow); overflow: hidden;
}
#sidebar.collapsed { transform: translateX(-100%); }
.sidebar-header {
  padding: 20px 20px 16px; text-align: center;
  border-bottom: 1px solid var(--border-sidebar); margin-top: var(--topbar-height);
}
.sidebar-logo { color: var(--accent-light); margin-bottom: 8px; }
.sidebar-title { font-size: 18px; font-weight: 600; letter-spacing: 2px; color: var(--text-sidebar-active); }
.sidebar-subtitle { font-size: 11px; font-weight: 400; letter-spacing: 1.5px; color: var(--text-sidebar-dim); text-transform: uppercase; margin-top: 2px; }

#sidebar-nav {
  flex: 1; overflow-y: auto; padding: 8px 0;
  scrollbar-width: thin; scrollbar-color: rgba(255,255,255,0.15) transparent;
}
#sidebar-nav::-webkit-scrollbar { width: 4px; }
#sidebar-nav::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.15); border-radius: 2px; }

.sidebar-footer {
  padding: 12px 20px; border-top: 1px solid var(--border-sidebar);
  display: flex; flex-direction: column; gap: 2px; font-size: 10px; color: var(--text-sidebar-dim);
}
.footer-license { opacity: 0.6; }

/* Sidebar tree */
.sidebar-group { margin: 2px 0; }
.sidebar-group-header {
  display: flex; align-items: center; gap: 8px;
  padding: 8px 20px; cursor: pointer; font-size: 12px; font-weight: 600;
  letter-spacing: 0.5px; color: var(--text-sidebar-dim); text-transform: uppercase;
  transition: color var(--transition-fast); user-select: none;
}
.sidebar-group-header:hover { color: var(--text-sidebar-active); }
.sidebar-group-header .chevron {
  width: 14px; height: 14px; flex-shrink: 0;
  transition: transform 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}
.sidebar-group-header .chevron.open { transform: rotate(90deg); }

.sidebar-group-children {
  overflow: hidden;
  max-height: 0;
  transition: max-height 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}
.sidebar-group-children.open { max-height: 8000px; }

.sidebar-item {
  display: flex; align-items: center; gap: 10px;
  padding: 7px 20px 7px 32px; cursor: pointer; font-size: 13px;
  color: var(--text-sidebar); transition: all var(--transition-fast);
  border-left: 3px solid transparent;
}
.sidebar-item:hover { background: var(--bg-sidebar-hover); color: var(--text-sidebar-active); }
.sidebar-item.active { background: var(--bg-sidebar-active); color: var(--text-sidebar-active); border-left-color: var(--accent-light); }
.sidebar-item .item-icon { width: 16px; height: 16px; flex-shrink: 0; opacity: 0.6; }
.sidebar-item .item-label { flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.sidebar-item .item-count { font-size: 10px; color: var(--text-sidebar-dim); flex-shrink: 0; }

/* Sidebar Overlay */
#sidebar-overlay {
  display: none; position: fixed; inset: 0; z-index: 190;
  background: rgba(0,0,0,0.3); backdrop-filter: blur(4px);
}
#sidebar-overlay.visible { display: block; }

/* ---------- Main Content ---------- */
#content {
  margin-left: var(--sidebar-width); margin-top: var(--topbar-height);
  flex: 1; min-height: calc(100vh - var(--topbar-height));
  transition: margin-left var(--transition-slow); padding: 40px; max-width: 900px;
}
#content.expanded { margin-left: 0; }

/* ---------- Welcome ---------- */
.welcome-hero { text-align: center; padding: 80px 20px 48px; }
.hero-icon { color: var(--accent); margin-bottom: 24px; opacity: 0.8; }
.hero-title { font-size: 42px; font-weight: 700; letter-spacing: 4px; color: var(--text-primary); margin-bottom: 12px; }
.hero-desc { font-size: 16px; color: var(--text-secondary); max-width: 480px; margin: 0 auto; line-height: 1.6; }

.welcome-guide { display: flex; flex-direction: column; gap: 16px; max-width: 400px; margin: 0 auto; padding: 24px; }
.guide-item {
  display: flex; align-items: center; gap: 14px;
  padding: 14px 18px; border-radius: var(--radius-md);
  background: var(--bg-secondary); border: 1px solid var(--border-light);
  font-size: 14px; color: var(--text-secondary);
  transition: all var(--transition-fast);
}
.guide-item:hover { box-shadow: var(--shadow-sm); transform: translateY(-1px); }
.guide-icon { color: var(--accent); flex-shrink: 0; }

/* ---------- Story Content ---------- */
.story-header { margin-bottom: 20px; }
.story-meta-row { display: flex; gap: 8px; margin-bottom: 12px; flex-wrap: wrap; }
.story-badge {
  display: inline-block; padding: 4px 12px; border-radius: 20px;
  font-size: 11px; font-weight: 500; letter-spacing: 0.3px;
  background: rgba(155,89,182,0.08); color: var(--accent-dark);
}
#story-title { font-size: 28px; font-weight: 700; letter-spacing: 1px; color: var(--text-primary); }

/* Entry Quick Nav */
.entry-quick-nav {
  display: flex; align-items: center; gap: 10px;
  margin-bottom: 20px; padding: 10px 16px;
  background: var(--bg-secondary); border-radius: var(--radius-md);
  border: 1px solid var(--border-light); flex-wrap: wrap;
}
.eqn-label { font-size: 12px; font-weight: 600; color: var(--text-secondary); flex-shrink: 0; }
.eqn-links { display: flex; flex-wrap: wrap; gap: 4px; }
.eqn-link {
  display: inline-block; padding: 4px 10px; border-radius: 14px;
  font-size: 12px; font-family: var(--font-mono); font-weight: 500;
  color: var(--text-secondary); background: transparent; border: none; cursor: pointer;
  transition: all var(--transition-fast);
}
.eqn-link:hover { background: rgba(155,89,182,0.08); color: var(--accent); }
.eqn-link.active { background: var(--accent); color: #fff; }

/* Entry Card */
.entry-card {
  background: var(--bg-secondary); border-radius: var(--radius-lg);
  border: 1px solid var(--border-light); margin-bottom: 24px; overflow: hidden;
  transition: box-shadow var(--transition-fast);
}
.entry-card:hover { box-shadow: var(--shadow-sm); }
.entry-header {
  padding: 20px 24px 0; display: flex; align-items: center;
  justify-content: space-between; flex-wrap: wrap; gap: 8px;
}
.entry-id { font-size: 18px; font-weight: 700; font-family: var(--font-mono); color: var(--accent); }
.entry-meta { display: flex; flex-wrap: wrap; gap: 8px; font-size: 11px; color: var(--text-tertiary); }
.entry-meta-item {
  padding: 3px 10px; border-radius: 12px;
  background: rgba(0,0,0,0.03); border: 1px solid var(--border-light);
}
.entry-body { padding: 20px 24px 24px; }
.entry-image-wrap {
  margin: 0 0 20px; border-radius: var(--radius-md); overflow: hidden;
  cursor: pointer; position: relative;
}
.entry-image-wrap img { width: 100%; display: block; border-radius: var(--radius-md); transition: transform 0.4s ease; }
.entry-image-wrap:hover img { transform: scale(1.02); }
.entry-image-wrap::after {
  content: ''; position: absolute; inset: 0; border-radius: var(--radius-md);
  background: transparent; transition: background var(--transition-fast); pointer-events: none;
}
.entry-image-wrap:hover::after { background: rgba(0,0,0,0.04); }
.image-caption {
  position: absolute; bottom: 10px; right: 12px;
  font-size: 10px; color: rgba(255,255,255,0.7);
  background: rgba(0,0,0,0.5); padding: 3px 8px; border-radius: 10px; letter-spacing: 0.5px;
}
.entry-paragraph { margin-bottom: 18px; line-height: 1.85; font-size: 15px; color: var(--text-primary); }
.entry-paragraph:last-child { margin-bottom: 0; }

/* Bottom Story Nav */
.story-nav {
  display: flex; align-items: center; justify-content: space-between;
  margin-top: 32px; padding: 16px 24px;
  background: var(--bg-secondary); border-radius: var(--radius-lg); border: 1px solid var(--border-light);
}
.nav-btn {
  display: flex; align-items: center; gap: 8px;
  padding: 10px 18px; border-radius: var(--radius-md);
  border: 1px solid var(--border-light); background: transparent;
  font-size: 13px; color: var(--text-primary); cursor: pointer;
  transition: all var(--transition-fast); font-family: var(--font-sans);
}
.nav-btn:hover:not(:disabled) { background: rgba(155,89,182,0.06); border-color: var(--accent); color: var(--accent); }
.nav-btn:disabled { opacity: 0.3; cursor: not-allowed; }
.nav-indicator { font-size: 13px; color: var(--text-tertiary); }

/* Lightbox */
.lightbox {
  display: none; position: fixed; inset: 0; z-index: 1000;
  background: rgba(0,0,0,0.92); align-items: center; justify-content: center; cursor: pointer;
}
.lightbox.open { display: flex; }
.lightbox-close {
  position: absolute; top: 20px; right: 20px; z-index: 1001;
  display: flex; align-items: center; justify-content: center;
  width: 44px; height: 44px; border: none; border-radius: 50%;
  background: rgba(255,255,255,0.1); color: #fff; cursor: pointer;
  transition: background var(--transition-fast);
}
.lightbox-close:hover { background: rgba(255,255,255,0.2); }
#lightbox-img { max-width: 90vw; max-height: 90vh; object-fit: contain; border-radius: var(--radius-sm); }

/* Fade-in */
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(16px); }
  to { opacity: 1; transform: translateY(0); }
}
.entry-card { animation: fadeUp 0.4s ease backwards; }

/* ---------- Responsive ---------- */
@media (max-width: 768px) {
  #sidebar { transform: translateX(-100%); }
  #sidebar.open { transform: translateX(0); }
  #sidebar-overlay.visible { display: block; }
  #content { margin-left: 0; padding: 20px 16px; }
  .hero-title { font-size: 32px; }
  .entry-card { border-radius: var(--radius-md); }
  .entry-header { padding: 16px 18px 0; }
  .entry-body { padding: 16px 18px 18px; }
  .story-nav { padding: 12px 16px; flex-wrap: wrap; gap: 8px; justify-content: center; }
  .nav-indicator { width: 100%; text-align: center; order: -1; }
}