/* ============================================================
   在线看课平台 — 管理后台主题 v2
   现代 · 响应式 · 高级质感
   ============================================================ */

/* ── CSS 变量系统 ── */
:root {
  --primary: #165dff;
  --primary-light: #e8f0ff;
  --primary-dark: #0e4fda;
  --primary-bg: rgba(22, 93, 255, 0.06);
  --success: #10b981;
  --success-light: #ecfdf5;
  --warning: #f59e0b;
  --warning-light: #fffbeb;
  --danger: #ef4444;
  --danger-light: #fef2f2;
  --info: #06b6d4;

  --text-1: #111827;
  --text-2: #374151;
  --text-3: #6b7280;
  --text-4: #9ca3af;
  --border: #e5e7eb;
  --border-light: #f3f4f6;
  --bg-page: #f0f2f5;
  --bg-card: #ffffff;
  --bg-hover: #f9fafb;
  --bg-input: #ffffff;

  --sidebar-w: 240px;
  --sidebar-bg: #1e293b;
  --sidebar-text: #cbd5e1;
  --sidebar-text-active: #ffffff;
  --sidebar-hover: #334155;
  --sidebar-active: #165dff;

  --radius: 8px;
  --radius-sm: 6px;
  --radius-lg: 12px;
  --shadow-sm: 0 1px 2px rgba(0,0,0,.05);
  --shadow: 0 1px 3px rgba(0,0,0,.08), 0 1px 2px rgba(0,0,0,.04);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,.08), 0 2px 4px -2px rgba(0,0,0,.05);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,.08), 0 4px 6px -4px rgba(0,0,0,.04);
  --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ── Reset ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { height: 100%; }
body {
  height: 100%;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', 'Helvetica Neue', sans-serif;
  background: var(--bg-page);
  color: var(--text-1);
  font-size: 14px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}
a { color: var(--primary); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--primary-dark); }

/* ── Login ── */
.login-body {
  display: flex; align-items: center; justify-content: center;
  min-height: 100vh;
  background: linear-gradient(135deg, #eef2ff 0%, #f0f2f5 50%, #ecfdf5 100%);
  padding: 20px;
}
.login-box {
  width: 400px; max-width: 100%;
  padding: 40px 36px;
  background: rgba(255,255,255,.85);
  backdrop-filter: blur(20px);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg), 0 0 0 1px rgba(255,255,255,.5);
}
.login-box h1 { font-size: 24px; text-align: center; color: var(--primary); margin-bottom: 2px; font-weight: 700; }
.login-desc { text-align: center; color: var(--text-3); margin-bottom: 28px; font-size: 14px; }
.login-box .form-group { margin-bottom: 20px; }
.login-box .form-group label { font-size: 13px; font-weight: 500; color: var(--text-2); margin-bottom: 6px; }

/* ── Layout ── */
.admin-wrap { display: flex; min-height: 100vh; position: relative; }

/* ── Sidebar ── */
.sidebar {
  width: var(--sidebar-w);
  background: var(--sidebar-bg);
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
  position: fixed;
  top: 0; left: 0;
  height: 100vh;
  z-index: 100;
  transition: transform var(--transition);
  overflow-y: auto;
  overflow-x: hidden;
}
.sidebar .logo {
  display: flex; align-items: center; gap: 10px;
  padding: 20px 20px 16px;
  font-size: 17px; font-weight: 700;
  color: #f1f5f9;
  border-bottom: 1px solid rgba(255,255,255,.06);
  white-space: nowrap;
}
.sidebar nav { flex: 1; padding: 8px 0 20px; overflow-y:auto; }
.sidebar nav a {
  display: flex; align-items: center; gap: 10px;
  padding: 10px 20px;
  color: var(--sidebar-text);
  font-size: 14px;
  transition: all var(--transition);
  border-left: 3px solid transparent;
  text-decoration: none;
}
.sidebar nav a:hover {
  background: var(--sidebar-hover);
  color: var(--sidebar-text-active);
}
.sidebar nav a.active {
  background: rgba(22, 93, 255, .15);
  color: var(--sidebar-text-active);
  border-left-color: var(--primary);
  font-weight: 500;
}
.sidebar-divider {
  height: 1px;
  background: rgba(255,255,255,.08);
  margin: 8px 16px;
}
.sidebar-cat {
  padding: 14px 20px 6px;
  font-size: 11px;
  font-weight: 600;
  color: rgba(255,255,255,.35);
  text-transform: uppercase;
  letter-spacing: 1px;
}
.sidebar-sub { padding-left: 32px !important; font-size: 13px !important; }

/* 侧栏遮罩（移动端） */
.sidebar-overlay {
  display: none;
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background: rgba(0,0,0,.4);
  z-index: 99;
  backdrop-filter: blur(2px);
  animation: fadeIn .2s ease;
}
.sidebar-overlay.show { display: block; }

/* 汉堡菜单按钮（固定在侧栏左上角） */
.sidebar-toggle {
  display: none;
  position: fixed;
  top: 12px; left: 12px;
  z-index: 101;
  width: 40px; height: 40px;
  border: none;
  border-radius: var(--radius);
  background: var(--bg-card);
  color: var(--text-2);
  font-size: 20px;
  cursor: pointer;
  box-shadow: var(--shadow);
  transition: all var(--transition);
  align-items: center;
  justify-content: center;
  line-height: 1;
}
.sidebar-toggle:hover { background: var(--primary-light); color: var(--primary); }
.sidebar-toggle.open { left: calc(var(--sidebar-w) + 12px); }
.sidebar-toggle .icon-close { display: none; }
.sidebar-toggle.open .icon-close { display: inline; }
.sidebar-toggle.open .icon-menu { display: none; }

/* ── 侧栏在移动端 ── */
@media (max-width: 767px) {
  .sidebar { transform: translateX(-100%); }
  .sidebar.open { transform: translateX(0); box-shadow: 4px 0 24px rgba(0,0,0,.2); }
  .sidebar-toggle { display: flex; }
  .sidebar.open ~ .sidebar-toggle { left: calc(var(--sidebar-w) + 12px); }
}

/* ── Main Area ── */
.main-area {
  flex: 1;
  display: flex;
  flex-direction: column;
  margin-left: var(--sidebar-w);
  min-width: 0;
  transition: margin-left var(--transition);
}
@media (max-width: 767px) {
  .main-area { margin-left: 0; }
}

/* ── Topbar ── */
.topbar {
  height: 56px;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 24px;
  flex-shrink: 0;
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(12px);
  background: rgba(255,255,255,.9);
}
.topbar h2 { font-size: 16px; font-weight: 600; }
.topbar .user-info { display: flex; align-items: center; gap: 14px; font-size: 13px; color: var(--text-3); }
.topbar .user-info a.logout { color: var(--text-4); transition: color var(--transition); }
.topbar .user-info a.logout:hover { color: var(--danger); }
/* 移动端 topbar 左侧留空间给汉堡按钮 */
@media (max-width: 767px) {
  .topbar { padding-left: 56px; }
}

/* ── Content ── */
.content {
  flex: 1;
  padding: 24px;
  overflow-y: auto;
}
@media (max-width: 480px) {
  .content { padding: 16px; }
}

/* ── Cards ── */
.card {
  background: var(--bg-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
  margin-bottom: 20px;
  transition: box-shadow var(--transition);
  overflow: hidden;
}
/* 表格在卡片内自动滚动 */
.card .table-wrap { margin: -4px -24px -8px; }
.card .table-wrap table { border-collapse: separate; border-spacing: 0; }
.card .table-wrap td, .card .table-wrap th { padding: 12px 16px; }
.card .table-wrap th:first-child { padding-left: 24px; }
.card .table-wrap td:first-child { padding-left: 24px; }
.card .table-wrap th:last-child { padding-right: 24px; }
.card .table-wrap td:last-child { padding-right: 24px; }
.card:hover { box-shadow: var(--shadow-md); }
.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
  flex-wrap: wrap;
  gap: 8px;
}
.card-header h3 {
  font-size: 16px;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 6px;
}
.card-actions { display: flex; gap: 8px; flex-wrap: wrap; }
@media (max-width: 480px) {
  .card { padding: 16px; }
  .card-header { flex-direction: column; align-items: stretch; }
  .card-actions { justify-content: flex-start; }
}

/* ── 统计卡片 ── */
.stat-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
  margin-bottom: 24px;
}
.stat-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 20px 16px;
  box-shadow: var(--shadow);
  text-align: center;
  transition: all var(--transition);
  border: 1px solid transparent;
}
.stat-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
  border-color: var(--border);
}
.stat-card .stat-icon { font-size: 28px; margin-bottom: 8px; }
.stat-card .number { font-size: 28px; font-weight: 700; line-height: 1.2; }
.stat-card .label  { color: var(--text-3); font-size: 13px; margin-top: 4px; }
.stat-card .sub    { font-size: 11px; color: var(--text-4); margin-top: 2px; }
@media (max-width: 900px) {
  .stat-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 480px) {
  .stat-grid { grid-template-columns: repeat(2, 1fr); gap: 10px; }
  .stat-card { padding: 14px 10px; }
  .stat-card .number { font-size: 22px; }
}

/* ── Dash Row ── */
.dash-row { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin-bottom: 24px; }
@media (max-width: 900px) {
  .dash-row { grid-template-columns: 1fr; }
}

/* ── 热门课程条 ── */
.hot-bar-wrap { display: flex; align-items: center; gap: 10px; margin-bottom: 8px; }
.hot-bar-wrap .rank { width: 22px; text-align: center; font-weight: 600; font-size: 13px; color: var(--text-3); flex-shrink: 0; }
.hot-bar-wrap .rank.top3 { color: var(--danger); }
.hot-bar-wrap .bar-bg { flex: 1; height: 24px; background: var(--border-light); border-radius: 4px; overflow: hidden; }
.hot-bar-wrap .bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary) 0%, #4b8bff 100%);
  border-radius: 4px;
  transition: width .6s cubic-bezier(.4,0,.2,1);
  min-width: 4px;
  display: flex;
  align-items: center;
  padding-left: 8px;
  font-size: 11px;
  color: #fff;
  white-space: nowrap;
}
.hot-bar-wrap .hot-info { width: 170px; flex-shrink: 0; font-size: 12px; color: var(--text-3); text-align: right; }
.hot-bar-wrap .hot-info strong { color: var(--text-1); }
@media (max-width: 480px) {
  .hot-bar-wrap .hot-info { width: 120px; }
}

/* ── Buttons ── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 8px 20px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  background: var(--bg-card);
  color: var(--text-2);
  transition: all var(--transition);
  line-height: 1.4;
  white-space: nowrap;
  text-decoration: none;
}
.btn:hover {
  border-color: var(--primary);
  color: var(--primary);
  background: var(--primary-bg);
}
.btn:active { transform: scale(.97); }

.btn-primary { background: var(--primary); color: #fff; border-color: var(--primary); }
.btn-primary:hover { background: var(--primary-dark); border-color: var(--primary-dark); color: #fff; }

.btn-success { background: var(--success); color: #fff; border-color: var(--success); }
.btn-success:hover { background: #059669; border-color: #059669; color: #fff; }

.btn-danger { background: var(--danger); color: #fff; border-color: var(--danger); }
.btn-danger:hover { background: #dc2626; border-color: #dc2626; color: #fff; }

.btn-warning { background: var(--warning); color: #fff; border-color: var(--warning); }
.btn-warning:hover { background: #d97706; border-color: #d97706; color: #fff; }

.btn-outline { background: transparent; color: var(--primary); border-color: var(--primary); }
.btn-outline:hover { background: var(--primary); color: #fff; }

.btn-sm { padding: 5px 12px; font-size: 12px; border-radius: 5px; }
.btn-lg { padding: 10px 24px; font-size: 15px; }
.btn-full { width: 100%; justify-content: center; padding: 10px 20px; }
.btn:disabled { opacity: .5; cursor: not-allowed; pointer-events: none; }

/* ── Forms ── */
.form-group { margin-bottom: 16px; }
.form-group label {
  display: block;
  font-size: 13px;
  font-weight: 500;
  color: var(--text-2);
  margin-bottom: 6px;
}
.form-group input[type="text"],
.form-group input[type="password"],
.form-group input[type="file"],
.form-group input[type="number"],
.form-group input[type="datetime-local"],
.form-group input[type="url"],
.form-group input[type="email"],
.form-group select,
.form-group textarea {
  width: 100%;
  padding: 9px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 14px;
  outline: none;
  transition: all var(--transition);
  background: var(--bg-input);
  color: var(--text-1);
}
.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(22, 93, 255, .12);
}
.form-group textarea { resize: vertical; min-height: 80px; }
.form-group input::placeholder,
.form-group textarea::placeholder { color: var(--text-4); }
.form-group .hint { font-size: 12px; color: var(--text-4); margin-top: 4px; }

/* ── Table ── */
.table-wrap {
  width: 100%;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin-bottom: 8px;
}
table {
  width: 100%;
  border-collapse: collapse;
  min-width: 600px;
}
table th, table td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border-light);
  font-size: 14px;
  line-height: 1.5;
}
table th {
  background: var(--bg-page);
  color: var(--text-2);
  font-weight: 500;
  font-size: 13px;
  white-space: nowrap;
}
table tr:hover td { background: var(--bg-hover); }
table tr:last-child td { border-bottom: none; }

/* 响应式：小屏表格用卡片布局 */
@media (max-width: 600px) {
  .table-wrap { margin-left: -16px; margin-right: -16px; }
  .table-wrap table { min-width: 520px; }
}

/* ── Tags / Badges ── */
.tag {
  display: inline-flex;
  align-items: center;
  padding: 2px 10px;
  border-radius: 100px;
  font-size: 12px;
  font-weight: 500;
  line-height: 1.6;
}
.tag-green { background: var(--success-light); color: #059669; }
.tag-blue  { background: var(--primary-light); color: var(--primary); }
.tag-gray  { background: var(--border-light); color: var(--text-3); }
.tag-orange{ background: var(--warning-light); color: #d97706; }
.tag-red   { background: var(--danger-light); color: #dc2626; }

/* ── Messages ── */
.msg {
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  margin-bottom: 16px;
  font-size: 13px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.msg.err { background: var(--danger-light); color: #dc2626; border: 1px solid #fecaca; }
.msg.ok  { background: var(--success-light); color: #059669; border: 1px solid #a7f3d0; }

/* ── Empty State ── */
.empty { text-align: center; padding: 48px 20px; color: var(--text-4); }
.empty p { margin-top: 8px; font-size: 13px; }
.empty .empty-icon { font-size: 48px; margin-bottom: 12px; opacity: .5; }

/* ── Pagination ── */
.pages {
  margin-top: 20px;
  display: flex;
  gap: 4px;
  justify-content: center;
  flex-wrap: wrap;
}
.pages a, .pages span {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 34px;
  height: 34px;
  padding: 0 8px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 13px;
  color: var(--text-2);
  transition: all var(--transition);
  text-decoration: none;
}
.pages a:hover { border-color: var(--primary); color: var(--primary); background: var(--primary-bg); }
.pages .current { background: var(--primary); color: #fff; border-color: var(--primary); }

/* ── Upload Zone ── */
.upload-zone {
  border: 2px dashed var(--border);
  border-radius: var(--radius);
  padding: 40px;
  text-align: center;
  cursor: pointer;
  transition: all var(--transition);
  margin-bottom: 16px;
  background: var(--bg-hover);
}
.upload-zone:hover { border-color: var(--primary); background: var(--primary-bg); }
.upload-zone.dragover { border-color: var(--primary); background: var(--primary-light); }
.upload-zone p { color: var(--text-3); margin-top: 8px; }

.progress-item { margin-bottom: 12px; }
.progress-item .info {
  display: flex;
  justify-content: space-between;
  font-size: 13px;
  margin-bottom: 4px;
}
.progress-item .info .name {
  color: var(--text-2);
  flex: 1;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.progress-item .info .pct { color: var(--primary); font-weight: 500; }
.progress-bar {
  height: 6px;
  background: var(--border-light);
  border-radius: 3px;
  overflow: hidden;
}
.progress-bar .fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), #4b8bff);
  border-radius: 3px;
  transition: width .3s ease;
  width: 0%;
}

/* ── Toggle Switch ── */
.toggle-wrap { display: flex; align-items: center; gap: 10px; }
.toggle-switch { position: relative; width: 44px; height: 24px; flex-shrink: 0; }
.toggle-switch input { opacity: 0; width: 0; height: 0; }
.toggle-slider {
  position: absolute; cursor: pointer; top: 0; left: 0; right: 0; bottom: 0;
  background: var(--border); border-radius: 12px; transition: .3s;
}
.toggle-slider::before {
  content: '';
  position: absolute;
  height: 18px; width: 18px;
  left: 3px; bottom: 3px;
  background: #fff;
  border-radius: 50%;
  transition: .3s;
  box-shadow: 0 1px 3px rgba(0,0,0,.15);
}
.toggle-switch input:checked + .toggle-slider { background: var(--success); }
.toggle-switch input:checked + .toggle-slider::before { transform: translateX(20px); }

/* ── Step Navigation ── */
.step-nav { display: flex; gap: 6px; margin-bottom: 24px; align-items: center; flex-wrap: wrap; }
.step-nav-item {
  display: inline-flex; align-items: center; gap: 8px;
  height: 48px; padding: 0 20px;
  border-radius: var(--radius-sm); font-size: 14px; font-weight: 500;
  text-decoration: none; transition: all var(--transition); cursor: pointer;
  white-space: nowrap;
}
.step-nav-item .s-icon { font-size: 18px; line-height: 1; }
.step-nav-item.active {
  background: var(--primary); color: #fff;
  box-shadow: 0 2px 8px rgba(22,93,255,.3);
}
.step-nav-item.inactive {
  background: var(--border-light); color: var(--text-2);
}
.step-nav-item.inactive:hover {
  background: var(--primary-light); color: var(--primary);
}
.step-nav-item.disabled {
  background: var(--border-light); color: var(--text-4); cursor: default;
}
.step-nav-arrow { color: var(--text-4); font-size: 16px; font-weight: 300; margin: 0 2px; }
@media (max-width: 600px) {
  .step-nav { gap: 4px; }
  .step-nav-item { padding: 0 12px; height: 40px; font-size: 12px; }
  .step-nav-arrow { font-size: 14px; }
}

/* ── Chapter Sort ── */
.chapter-list { list-style: none; }
.chapter-item {
  display: flex; align-items: center; gap: 12px;
  padding: 12px 16px;
  background: var(--bg-hover);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  margin-bottom: 8px;
  cursor: grab;
  transition: all var(--transition);
}
.chapter-item:hover { border-color: var(--primary); background: var(--primary-bg); }
.chapter-item.dragging { opacity: .5; box-shadow: var(--shadow-md); }
.chapter-item .drag-handle { cursor: grab; color: var(--text-4); font-size: 18px; user-select: none; }
.chapter-item .title { flex: 1; min-width: 0; }
.chapter-item .actions { display: flex; gap: 6px; flex-shrink: 0; flex-wrap: wrap; }
.chapter-item input.edit-title { 
  flex: 1; padding: 6px 10px; border: 1px solid var(--border);
  border-radius: var(--radius-sm); font-size: 13px; outline: none;
}
.chapter-item input.edit-title:focus { border-color: var(--primary); }
.chapter-item .chapter-info { display: flex; align-items: center; gap: 6px; flex-shrink: 0; min-width: 110px; }
.chapter-item .chapter-info .info-tag { color: var(--text-3); font-size: 12px; white-space: nowrap; }
.chapter-item .chapter-info .info-divider { color: var(--border); font-size: 12px; }
@media (max-width: 600px) {
  .chapter-item { flex-wrap: wrap; }
  .chapter-item .actions { width: 100%; justify-content: flex-end; margin-top: 4px; }
  .chapter-item .chapter-info { min-width: 80px; }
}

/* ── Cover Upload 4:3 ── */
.cover-upload-wrap { display: flex; gap: 20px; align-items: flex-start; flex-wrap: wrap; }
.cover-upload-zone {
  width: 280px; height: 210px;
  border: 2px dashed var(--border); border-radius: var(--radius);
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  cursor: pointer; transition: all var(--transition); background: var(--bg-hover); flex-shrink: 0;
  position: relative; overflow: hidden;
}
.cover-upload-zone:hover { border-color: var(--primary); background: var(--primary-bg); }
.cover-upload-zone.dragover { border-color: var(--primary); background: var(--primary-light); }
.cover-upload-zone .plus { font-size: 64px; color: var(--text-4); line-height: 1; font-weight: 200; text-align: center; }
.cover-upload-zone .label { font-size: 14px; color: var(--text-4); margin-top: 10px; text-align: center; }
.cover-upload-zone .hint { font-size: 11px; color: var(--border); margin-top: 6px; text-align: center; }
.cover-upload-zone img { position: absolute; top: 0; left: 0; width: 100%; height: 100%; object-fit: cover; }
.cover-preview { display: none; }
.cover-actions {
  position: absolute; bottom: 0; left: 0; right: 0; display: flex; gap: 0;
}
.cover-actions .cover-btn {
  flex: 1; padding: 8px; text-align: center; font-size: 13px;
  color: #fff; background: rgba(0,0,0,.55); text-decoration: none;
  transition: background .25s; cursor: pointer;
}
.cover-actions .cover-btn:hover { background: rgba(0,0,0,.75); }
.cover-actions .cover-btn-del:hover { background: rgba(220,38,38,.85); }
.cover-info { flex: 1; min-width: 200px; }
.cover-info .size-hint { font-size: 12px; color: var(--text-4); margin-top: 6px; }
@media (max-width: 480px) {
  .cover-upload-zone { width: 100%; height: 200px; }
}

/* ── 课程管理网格（course/index.php） ── */
.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 16px;
}
.course-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
  transition: all var(--transition);
  min-width: 0;
  border: 1px solid transparent;
}
.course-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
  border-color: var(--border);
}
.course-card .card-cover {
  width: 100%; aspect-ratio: 4/3; object-fit: cover;
  background: var(--border-light); display: block;
  transition: transform .4s ease;
}
.course-card:hover .card-cover { transform: scale(1.05); }
.course-card .card-cover-placeholder {
  width: 100%; aspect-ratio: 4/3;
  background: linear-gradient(135deg, var(--primary-light), #d6e4ff);
  display: flex; align-items: center; justify-content: center; font-size: 40px;
}
.course-card .card-body { padding: 16px 18px 14px; }
.course-card .card-title { font-size: 15px; font-weight: 600; margin-bottom: 4px; }
.course-card .card-title a { color: var(--text-1); }
.course-card .card-title a:hover { color: var(--primary); }
.course-card .card-meta {
  display: flex; gap: 14px; font-size: 13px; color: var(--text-3); margin-top: 8px;
  flex-wrap: wrap;
}
.course-card .card-meta span { display: flex; align-items: center; gap: 4px; }
.course-card .card-actions {
  display: flex; gap: 6px;
  padding: 10px 18px;
  border-top: 1px solid var(--border-light);
  flex-wrap: wrap;
}
.course-card .card-actions .btn-sm { font-size: 12px; padding: 4px 10px; }
@media (max-width: 480px) {
  .course-grid { grid-template-columns: repeat(2, 1fr); gap: 10px; }
  .course-card .card-body { padding: 12px 14px 10px; }
  .course-card .card-title { font-size: 13px; }
}
@media (max-width: 380px) {
  .course-grid { grid-template-columns: 1fr; }
}

/* ── Dropdown Categories ── */
.cat-select { display: flex; gap: 8px; flex-wrap: wrap; }
.cat-select select { flex: 1; min-width: 120px; }

/* ── Setting section ── */
.setting-section { margin-bottom: 28px; padding-bottom: 20px; border-bottom: 1px solid var(--border-light); }
.setting-section:last-child { border-bottom: none; margin-bottom: 0; padding-bottom: 0; }
.setting-section h4 { font-size: 15px; font-weight: 600; margin-bottom: 4px; }
.setting-section .hint { font-size: 12px; color: var(--text-4); margin-bottom: 12px; }
.logo-preview {
  width: 120px; height: 40px; border-radius: var(--radius-sm);
  border: 1px solid var(--border); display: flex;
  align-items: center; justify-content: center; overflow: hidden; margin-top: 8px;
  background: var(--bg-hover);
}
.logo-preview img { max-width: 100%; max-height: 100%; object-fit: contain; }

/* ── SMS Tabs ── */
.sms-tabs {
  display: flex; gap: 0;
  border-bottom: 2px solid var(--border);
  margin-bottom: 24px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}
.sms-tab {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 12px 20px; font-size: 14px;
  color: var(--text-3); text-decoration: none;
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
  transition: all var(--transition);
  cursor: pointer;
  white-space: nowrap;
}
.sms-tab:hover { color: var(--primary); }
.sms-tab.active { color: var(--primary); border-bottom-color: var(--primary); font-weight: 500; }
.sms-panel { display: none; }
.sms-panel.active { display: block; }
.sms-info {
  padding: 14px 18px;
  background: var(--primary-bg);
  border: 1px solid var(--primary-light);
  border-radius: var(--radius-sm);
  font-size: 13px;
  color: var(--text-2);
  margin-bottom: 20px;
  line-height: 1.8;
}
.field-row { margin-bottom: 16px; }
.field-row label { display: block; font-size: 13px; color: var(--text-2); margin-bottom: 4px; font-weight: 500; }
.field-row input, .field-row select {
  width: 100%; max-width: 450px;
  padding: 9px 12px; border: 1px solid var(--border);
  border-radius: var(--radius-sm); font-size: 14px; outline: none;
}
.field-row input:focus, .field-row select:focus {
  border-color: var(--primary); box-shadow: 0 0 0 3px rgba(22,93,255,.12);
}
.field-row .hint { font-size: 12px; color: var(--text-4); margin-top: 4px; }
.two-cols { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; max-width: 600px; }
@media (max-width: 600px) { .two-cols { grid-template-columns: 1fr; } }

/* ── Scan Duration ── */
.scan-wrap { max-width: 700px; margin: 0 auto; }
.scan-wrap .count { font-size: 24px; font-weight: 700; color: var(--primary); }
.scan-wrap .count.zero { color: var(--success); }
.error-list { margin-top: 12px; font-size: 13px; color: var(--danger); }
.error-list li { padding: 4px 0; }

/* ── Responsive Table ── */
.table-responsive { width:100%; overflow-x:auto; -webkit-overflow-scrolling:touch; }
.table-responsive table { min-width:750px; }

/* ── Animations ── */
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

/* ── Utility ── */
.flex { display: flex; }
.flex-wrap { flex-wrap: wrap; }
.flex-1 { flex: 1; min-width: 0; }
.items-center { align-items: center; }
.gap-8  { gap: 8px; }
.gap-12 { gap: 12px; }
.gap-16 { gap: 16px; }
.mt-16 { margin-top: 16px; }
.mt-24 { margin-top: 24px; }
.mb-16 { margin-bottom: 16px; }
.text-center { text-align: center; }
.text-right { text-align: right; }
.text-secondary { color: var(--text-3); }
.text-sm { font-size: 13px; }
.text-xs { font-size: 12px; }
.font-medium { font-weight: 500; }
.font-mono { font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace; }
.w-full { width: 100%; }
.max-w-600 { max-width: 600px; }
.max-w-700 { max-width: 700px; }
.max-w-900 { max-width: 900px; }

/* ============================================================
   字体大小切换（后台通用）
   ============================================================ */
html.font-size-large {
  --font-base: 15px;
}
html.font-size-xlarge {
  --font-base: 17px;
}
html.font-size-large .content { font-size: 15px; }
html.font-size-xlarge .content { font-size: 17px; }
html.font-size-large table th, html.font-size-large table td { font-size: 14px; }
html.font-size-xlarge table th, html.font-size-xlarge table td { font-size: 16px; }
html.font-size-large .btn-sm { font-size: 12px; padding: 6px 14px; }
html.font-size-xlarge .btn-sm { font-size: 14px; padding: 8px 16px; }