/* ===== CSS Variables ===== */
:root {
  --sidebar-width: 240px;
  --sidebar-collapsed: 0px;
  --header-height: 56px;
  --mobile-nav-height: 60px;
  --color-primary: #2c3e50;
  --color-primary-light: #34495e;
  --color-accent: #3498db;
  --color-accent-hover: #2980b9;
  --color-bg: #f0f2f5;
  --color-card: #ffffff;
  --color-text: #2c3e50;
  --color-text-secondary: #7f8c8d;
  --color-border: #e8ecf1;
  --color-success: #27ae60;
  --color-warning: #f39c12;
  --color-danger: #e74c3c;
  --color-info: #3498db;
  --radius: 8px;
  --radius-sm: 4px;
  --shadow: 0 2px 8px rgba(0,0,0,0.08);
  --shadow-lg: 0 4px 16px rgba(0,0,0,0.12);
  --transition: 0.25s ease;
}

/* ===== Reset ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 14px; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  color: var(--color-text);
  background: var(--color-bg);
  display: flex;
  min-height: 100vh;
  overflow-x: hidden;
}
a { text-decoration: none; color: inherit; }
button { cursor: pointer; border: none; background: none; font: inherit; }
table { border-collapse: collapse; width: 100%; }

/* ===== Sidebar (PC) ===== */
.sidebar {
  width: var(--sidebar-width);
  background: var(--color-primary);
  color: #fff;
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0; left: 0; bottom: 0;
  z-index: 100;
  transition: width var(--transition);
  overflow-y: auto;
  overflow-x: hidden;
}
.sidebar::-webkit-scrollbar { width: 4px; }
.sidebar::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.2); border-radius: 4px; }

.sidebar-header {
  padding: 20px 16px 12px;
  border-bottom: 1px solid rgba(255,255,255,0.1);
  flex-shrink: 0;
}
.sidebar-title {
  font-size: 18px;
  font-weight: 600;
  letter-spacing: 1px;
  white-space: nowrap;
}

/* ===== Sidebar Navigation ===== */
.sidebar-nav { padding: 8px 0; flex: 1; }
.nav-group { margin-bottom: 2px; }

.nav-item {
  display: flex;
  align-items: center;
  padding: 10px 16px;
  cursor: pointer;
  transition: background var(--transition);
  white-space: nowrap;
  user-select: none;
  font-size: 13px;
  border-radius: 0;
}
.nav-item:hover { background: rgba(255,255,255,0.08); }
.nav-item.active { background: rgba(255,255,255,0.15); }

.nav-icon { margin-right: 10px; font-size: 16px; flex-shrink: 0; }
.nav-label { flex: 1; }
.nav-arrow {
  font-size: 14px;
  transition: transform var(--transition);
  opacity: 0.6;
}
.nav-item.expanded > .nav-arrow { transform: rotate(90deg); }

/* Sub navigation */
.nav-sub {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
  background: rgba(0,0,0,0.15);
}
.nav-sub.expanded { max-height: 600px; }

/* Second-level group */
.nav-sub-group { margin-bottom: 1px; }
.nav-sub-parent {
  padding-left: 42px;
  font-size: 12.5px;
  font-weight: 500;
  opacity: 0.9;
}
.nav-sub-parent .nav-arrow { font-size: 12px; }

/* Leaf items */
.nav-sub-leaf .nav-item {
  padding-left: 58px;
  font-size: 12.5px;
  opacity: 0.85;
}
.nav-sub-leaf .nav-item:hover { opacity: 1; }
.nav-sub-leaf .nav-item.active {
  background: var(--color-accent);
  opacity: 1;
}

/* ===== Main Content ===== */
.main-content {
  margin-left: var(--sidebar-width);
  flex: 1;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: margin-left var(--transition);
}

.page-header {
  height: var(--header-height);
  background: var(--color-card);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  padding: 0 24px;
  position: sticky;
  top: 0;
  z-index: 50;
  box-shadow: 0 1px 4px rgba(0,0,0,0.04);
}
.page-header h2 { font-size: 16px; font-weight: 600; }
.breadcrumb {
  margin-left: 16px;
  font-size: 12px;
  color: var(--color-text-secondary);
}
.breadcrumb span + span::before { content: " / "; }

.mobile-menu-btn {
  display: none;
  font-size: 20px;
  margin-right: 12px;
  padding: 4px;
}

.page-content {
  flex: 1;
  padding: 24px;
}

/* ===== Cards ===== */
.card {
  background: var(--color-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
  margin-bottom: 16px;
}
.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 16px;
}
.card-title {
  font-size: 15px;
  font-weight: 600;
  color: var(--color-text);
}
.card-actions { display: flex; gap: 8px; }

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  font-weight: 500;
  transition: all var(--transition);
}
.btn-primary { background: var(--color-accent); color: #fff; }
.btn-primary:hover { background: var(--color-accent-hover); }
.btn-success { background: var(--color-success); color: #fff; }
.btn-success:hover { opacity: 0.9; }
.btn-warning { background: var(--color-warning); color: #fff; }
.btn-warning:hover { opacity: 0.9; }
.btn-outline {
  border: 1px solid var(--color-border);
  color: var(--color-text);
  background: #fff;
}
.btn-outline:hover { border-color: var(--color-accent); color: var(--color-accent); }
.btn-sm { padding: 4px 10px; font-size: 12px; }

/* ===== Tables ===== */
.table-wrapper {
  overflow-x: auto;
  border-radius: var(--radius);
}
table {
  width: 100%;
  font-size: 13px;
}
thead th {
  background: var(--color-bg);
  padding: 10px 12px;
  text-align: left;
  font-weight: 600;
  color: var(--color-text-secondary);
  border-bottom: 2px solid var(--color-border);
  white-space: nowrap;
}
tbody td {
  padding: 10px 12px;
  border-bottom: 1px solid var(--color-border);
}
tbody tr:hover { background: rgba(52,152,219,0.04); }

/* ===== Status Tags ===== */
.tag {
  display: inline-block;
  padding: 2px 8px;
  border-radius: 10px;
  font-size: 11px;
  font-weight: 500;
}
.tag-success { background: #e8f8ef; color: var(--color-success); }
.tag-warning { background: #fef5e7; color: var(--color-warning); }
.tag-danger { background: #fde8e8; color: var(--color-danger); }
.tag-info { background: #e8f4fd; color: var(--color-info); }

/* ===== Equipment Cards Grid ===== */
.equipment-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}
.equipment-card {
  background: var(--color-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
  transition: transform var(--transition), box-shadow var(--transition);
}
.equipment-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}
.equipment-card-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
}
.equipment-card-icon {
  width: 44px; height: 44px;
  background: var(--color-bg);
  border-radius: 10px;
  display: flex; align-items: center; justify-content: center;
  font-size: 22px;
}
.equipment-card-name { font-weight: 600; font-size: 14px; }
.equipment-card-model { font-size: 12px; color: var(--color-text-secondary); }
.equipment-card-body { font-size: 12.5px; color: var(--color-text-secondary); }
.equipment-card-body p { margin-bottom: 4px; }
.equipment-card-footer {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--color-border);
  display: flex;
  justify-content: flex-end;
  gap: 8px;
}

/* ===== Kanban Board ===== */
.kanban {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 16px;
}
.kanban-column {
  background: var(--color-bg);
  border-radius: var(--radius);
  padding: 16px;
}
.kanban-column-title {
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 12px;
  display: flex; align-items: center; gap: 8px;
}
.kanban-column-title .count {
  background: var(--color-accent);
  color: #fff;
  font-size: 11px;
  padding: 1px 7px;
  border-radius: 10px;
}
.kanban-card {
  background: var(--color-card);
  border-radius: var(--radius-sm);
  padding: 12px;
  margin-bottom: 8px;
  box-shadow: 0 1px 3px rgba(0,0,0,0.06);
}
.kanban-card-title { font-weight: 500; font-size: 13px; margin-bottom: 4px; }
.kanban-card-meta { font-size: 11px; color: var(--color-text-secondary); }

/* ===== Info Grid (Contacts / Academic) ===== */
.info-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 12px;
}
.info-card {
  background: var(--color-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 16px;
  transition: transform var(--transition);
}
.info-card:hover { transform: translateY(-1px); }
.info-card-name { font-weight: 600; font-size: 14px; margin-bottom: 8px; }
.info-card-detail { font-size: 12.5px; color: var(--color-text-secondary); margin-bottom: 4px; }

/* ===== Schedule Calendar Grid ===== */
.schedule-grid {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 1px;
  background: var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
}
.schedule-cell {
  background: var(--color-card);
  padding: 8px;
  min-height: 80px;
  font-size: 12px;
}
.schedule-cell-header {
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-bottom: 4px;
}
.schedule-cell-item {
  padding: 2px 6px;
  background: var(--color-bg);
  border-radius: 3px;
  margin-bottom: 2px;
  font-size: 11px;
}

/* ===== Search & Filter Bar ===== */
.toolbar {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}
.search-input {
  padding: 7px 12px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-size: 13px;
  outline: none;
  transition: border-color var(--transition);
  min-width: 200px;
}
.search-input:focus { border-color: var(--color-accent); }
.select-input {
  padding: 7px 12px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-size: 13px;
  outline: none;
  background: #fff;
  color: var(--color-text);
}

/* ===== Empty State ===== */
.empty-state {
  text-align: center;
  padding: 48px 24px;
  color: var(--color-text-secondary);
}
.empty-state-icon { font-size: 40px; margin-bottom: 12px; opacity: 0.4; }
.empty-state-text { font-size: 14px; }

/* ===== Stats Row ===== */
.stats-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 16px;
  margin-bottom: 24px;
}
.stat-card {
  background: var(--color-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 16px;
  display: flex;
  align-items: center;
  gap: 12px;
}
.stat-icon {
  width: 40px; height: 40px;
  border-radius: 10px;
  display: flex; align-items: center; justify-content: center;
  font-size: 18px;
}
.stat-icon.blue { background: #e8f4fd; }
.stat-icon.green { background: #e8f8ef; }
.stat-icon.orange { background: #fef5e7; }
.stat-icon.purple { background: #f0e8fd; }
.stat-value { font-size: 22px; font-weight: 700; }
.stat-label { font-size: 12px; color: var(--color-text-secondary); }

/* ===== Mobile Bottom Nav ===== */
.mobile-nav {
  display: none;
  position: fixed;
  bottom: 0; left: 0; right: 0;
  height: var(--mobile-nav-height);
  background: var(--color-card);
  border-top: 1px solid var(--color-border);
  z-index: 90;
  box-shadow: 0 -2px 8px rgba(0,0,0,0.06);
}
.mobile-nav-items {
  display: flex;
  height: 100%;
}
.mobile-nav-item {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  cursor: pointer;
  transition: color var(--transition);
  color: var(--color-text-secondary);
}
.mobile-nav-item.active { color: var(--color-accent); }
.mobile-nav-icon { font-size: 18px; }
.mobile-nav-label { font-size: 10px; }

/* ===== Mobile Sub-nav Overlay ===== */
.mobile-subnav-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  z-index: 200;
  justify-content: flex-end;
  flex-direction: column;
}
.mobile-subnav-overlay.show { display: flex; }

.mobile-subnav {
  background: var(--color-card);
  border-radius: 16px 16px 0 0;
  max-height: 70vh;
  display: flex;
  flex-direction: column;
  animation: slideUp 0.3s ease;
}
@keyframes slideUp {
  from { transform: translateY(100%); }
  to { transform: translateY(0); }
}
.mobile-subnav-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  border-bottom: 1px solid var(--color-border);
  font-weight: 600;
  font-size: 15px;
}
.mobile-subnav-close { font-size: 20px; padding: 4px; color: var(--color-text-secondary); }
.mobile-subnav-body { padding: 8px 0; overflow-y: auto; }

.mobile-subnav-group-title {
  padding: 8px 20px 4px;
  font-size: 11px;
  font-weight: 600;
  color: var(--color-text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.mobile-subnav-item {
  display: block;
  padding: 12px 20px;
  font-size: 14px;
  cursor: pointer;
  transition: background var(--transition);
}
.mobile-subnav-item:hover { background: var(--color-bg); }
.mobile-subnav-item.active { color: var(--color-accent); font-weight: 500; }

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .sidebar { transform: translateX(-100%); }
  .sidebar.mobile-open { transform: translateX(0); }
  .main-content { margin-left: 0; }
  .mobile-menu-btn { display: block; }
  .mobile-nav { display: block; }
  .page-content { padding: 16px; padding-bottom: calc(var(--mobile-nav-height) + 16px); }
  .page-header { padding: 0 16px; }
  .equipment-grid { grid-template-columns: 1fr; }
  .kanban { grid-template-columns: 1fr; }
  .stats-row { grid-template-columns: repeat(2, 1fr); }
  .search-input { min-width: 0; flex: 1; }
}

@media (min-width: 769px) {
  .mobile-subnav-overlay { display: none !important; }
}