:root {
  --bg: #f0f5ff;
  --paper: #ffffff;
  --paper-strong: #ffffff;
  --ink: #1e293b;
  --subtle: #64748b;
  --line: rgba(30, 41, 59, 0.12);
  --brand: #2563eb;
  --brand-dark: #1d4ed8;
  --brand-light: #dbeafe;
  --danger: #b91c1c;
  --success: #166534;
  --shadow: 0 8px 32px rgba(0, 0, 0, 0.07);
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
}

a {
  color: inherit;
}

button,
input,
textarea,
select {
  font: inherit;
}

button {
  cursor: pointer;
}

.page-shell {
  max-width: 1320px;
  margin: 0 auto;
  padding: 28px 18px 60px;
}

.hero {
  position: relative;
  overflow: hidden;
  padding: 22px 24px;
  border-radius: 22px;
  background: linear-gradient(135deg, #1e40af 0%, #3b82f6 100%);
  color: #fff;
  box-shadow: var(--shadow);
  margin-bottom: 18px;
}

.hero::after {
  content: "";
  position: absolute;
  width: 360px;
  height: 360px;
  right: -80px;
  top: -120px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(255, 255, 255, 0.12), transparent 70%);
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 8px 14px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.18);
  border: 1px solid rgba(255, 255, 255, 0.30);
  font-size: 13px;
  letter-spacing: 0.08em;
}

.hero h1,
.hero h2 {
  margin: 18px 0 10px;
  font-size: clamp(30px, 5vw, 52px);
  line-height: 1.05;
}

.hero p {
  max-width: 760px;
  color: rgba(255, 255, 255, 0.90);
  line-height: 1.75;
}

.credentials {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 12px;
  margin-top: 22px;
}

.credential-card {
  padding: 16px;
  border-radius: 16px;
  background: rgba(255, 255, 255, 0.15);
  border: 1px solid rgba(255, 255, 255, 0.25);
  color: #fff;
}

.credential-card strong {
  display: block;
  margin-bottom: 6px;
}

.credential-card .muted {
  color: rgba(255, 255, 255, 0.80);
}

.paper-card,
.panel,
.metric-card,
.topic-card,
.task-card,
.store-card,
.question-card,
.notification-card,
.summary-card,
.order-card {
  border-radius: 22px;
  border: 1px solid var(--line);
  background: var(--paper);
  box-shadow: var(--shadow);
}

.paper-card,
.panel {
  padding: 22px;
}

.auth-grid,
.dashboard-grid {
  display: grid;
  gap: 18px;
  margin-top: 20px;
}

.auth-grid {
  grid-template-columns: minmax(0, 1.1fr) minmax(320px, 420px);
}

.dashboard-grid {
  /* 单栏全宽布局 */
  max-width: 1200px;
  margin: 0 auto;
}

/* ========== 顶部导航栏 ========== */
.top-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  gap: 4px;
  padding: 0 18px;
  height: 56px;
  background: rgba(255, 255, 255, 0.95);
  -webkit-backdrop-filter: blur(12px);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--line);
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.04);
}

.nav-brand {
  width: 36px;
  height: 36px;
  display: grid;
  place-items: center;
  border-radius: 10px;
  background: linear-gradient(135deg, var(--brand) 0%, #60a5fa 100%);
  color: #fff;
  font-size: 18px;
  font-weight: 700;
  margin-right: 12px;
  flex-shrink: 0;
}

.nav-links {
  display: flex;
  gap: 2px;
  overflow-x: auto;
  flex: 1;
  scrollbar-width: none;
}

.nav-links::-webkit-scrollbar {
  display: none;
}

.nav-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 14px;
  border: none;
  border-radius: 10px;
  background: transparent;
  color: var(--subtle);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  white-space: nowrap;
  transition: background 0.15s, color 0.15s;
  position: relative;
}

.nav-link:hover {
  background: var(--brand-light);
  color: var(--brand-dark);
}

.nav-link.active {
  background: var(--brand-light);
  color: var(--brand);
  font-weight: 600;
}

.nav-link.active::after {
  content: "";
  position: absolute;
  bottom: -1px;
  left: 14px;
  right: 14px;
  height: 3px;
  border-radius: 3px 3px 0 0;
  background: var(--brand);
}

.nav-link .nav-icon {
  font-size: 16px;
}

/* 更多下拉（复用 tab-dropdown 样式结构） */
.nav-more-wrap {
  position: relative;
  flex-shrink: 0;
}

.nav-more-btn {
  display: inline-flex;
  align-items: center;
  padding: 8px 12px;
  border: none;
  border-radius: 10px;
  background: transparent;
  color: var(--subtle);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.nav-more-btn:hover {
  background: var(--brand-light);
  color: var(--brand-dark);
}

.nav-more-btn.active {
  background: var(--brand-light);
  color: var(--brand);
  font-weight: 600;
}

/* 右侧用户区域 */
.nav-user {
  position: relative;
  margin-left: auto;
  flex-shrink: 0;
}

.nav-user-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border: none;
  border-radius: 10px;
  background: transparent;
  color: var(--ink);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s;
}

.nav-user-btn:hover {
  background: #f1f5f9;
}

.nav-user-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  min-width: 180px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 14px;
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.12);
  z-index: 110;
  padding: 6px;
  display: none;
}

.nav-user-dropdown.show {
  display: block;
  animation: fadeIn 0.15s ease;
}

.nav-user-dropdown button {
  display: block;
  width: 100%;
  text-align: left;
  padding: 10px 14px;
  border: none;
  border-radius: 8px;
  background: transparent;
  color: var(--ink);
  font-size: 14px;
  cursor: pointer;
  transition: background 0.12s;
}

.nav-user-dropdown button:hover {
  background: var(--brand-light);
  color: var(--brand-dark);
}

/* ========== 设置面板 ========== */
.settings-panel {
  padding: 22px;
}

.settings-panel .settings-section {
  margin-bottom: 24px;
}

.settings-panel .settings-section:last-child {
  margin-bottom: 0;
}

.settings-info-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 12px;
}

.settings-info-item {
  padding: 14px;
  border-radius: 14px;
  background: #f8fafc;
  border: 1px solid #e2e8f0;
}

.settings-info-item .muted {
  font-size: 12px;
}

.settings-info-item strong {
  display: block;
  margin-top: 4px;
  font-size: 15px;
}

.muted {
  color: var(--subtle);
}

.stat-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(170px, 1fr));
  gap: 14px;
  margin-top: 16px;
}

.metric-card {
  padding: 18px;
}

.metric-card .muted {
  color: var(--subtle);
}

.metric-card strong {
  display: block;
  margin-top: 10px;
  font-size: 30px;
  color: var(--ink);
}

.tab-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 18px 0;
  position: relative;
}

/* 更多 下拉菜单 */
.tab-more-wrap {
  position: relative;
}

.tab-more-btn {
  border: 2px solid var(--brand);
  border-radius: 999px;
  padding: 11px 18px;
  font-weight: 600;
  background: #ffffff;
  color: var(--brand);
  cursor: pointer;
  transition: transform 0.16s ease, box-shadow 0.16s ease, background 0.16s ease;
}

.tab-more-btn:hover {
  transform: translateY(-1px);
}

.tab-more-btn.active {
  background: var(--brand);
  border-color: var(--brand-dark);
  color: #fff;
  box-shadow: 0 4px 16px rgba(37, 99, 235, 0.25);
}

.tab-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  min-width: 180px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.12);
  z-index: 100;
  padding: 8px;
  display: none;
}

.tab-dropdown.show {
  display: block;
  animation: fadeIn 0.15s ease;
}

.tab-dropdown-item {
  display: block;
  width: 100%;
  text-align: left;
  padding: 10px 14px;
  border: none;
  border-radius: 10px;
  background: transparent;
  color: var(--ink);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.12s;
}

.tab-dropdown-item:hover {
  background: var(--brand-light);
  color: var(--brand-dark);
}

.tab-dropdown-item.active {
  background: var(--brand);
  color: #fff;
}

.tab-badge-beta {
  display: inline-block;
  margin-left: 6px;
  padding: 2px 6px;
  border-radius: 6px;
  background: #f1f5f9;
  color: #94a3b8;
  font-size: 11px;
  font-weight: 600;
}

.tab-button,
.button,
.ghost-button,
.danger-button {
  border: 2px solid transparent;
  border-radius: 999px;
  padding: 11px 18px;
  font-weight: 600;
  transition: transform 0.16s ease, box-shadow 0.16s ease, background 0.16s ease;
}

.tab-button,
.ghost-button {
  background: #ffffff;
  border-color: var(--brand);
  color: var(--brand);
}

.tab-button.active,
.button {
  background: var(--brand);
  border-color: var(--brand-dark);
  color: #fff;
  box-shadow: 0 4px 16px rgba(37, 99, 235, 0.25);
}

.ghost-button {
  background: #ffffff;
  border-color: var(--brand);
  color: var(--brand);
}

.danger-button {
  background: #ffffff;
  border-color: var(--danger);
  color: var(--danger);
}

.tab-button:hover,
.button:hover,
.ghost-button:hover,
.danger-button:hover {
  transform: translateY(-1px);
}

.hidden {
  display: none !important;
}

.focus-overlay {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.form-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}

.form-grid .full-span {
  grid-column: 1 / -1;
}

.field {
  display: grid;
  gap: 8px;
}

.field label {
  font-size: 14px;
  color: var(--subtle);
}

.input,
.textarea,
.select {
  width: 100%;
  padding: 12px 14px;
  border-radius: 16px;
  border: 1px solid #cbd5e1;
  background: #ffffff;
}

.textarea {
  min-height: 120px;
  font-family: inherit;
  resize: vertical;
}

.checkbox-wrap {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.checkbox-chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 12px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: #ffffff;
}

.list-grid {
  display: grid;
  gap: 14px;
  margin-top: 18px;
}

.task-card,
.question-card,
.topic-card,
.summary-card,
.notification-card,
.store-card,
.order-card {
  padding: 18px;
}

.card-head {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: start;
}

.badge {
  display: inline-flex;
  align-items: center;
  padding: 6px 10px;
  border-radius: 999px;
  background: var(--brand-light);
  color: var(--brand-dark);
  font-size: 12px;
  font-weight: 600;
  border: 1px solid rgba(37, 99, 235, 0.20);
}

.badge-brand {
  background: #fef3c7;
  color: #92400e;
  border-color: rgba(146, 64, 14, 0.20);
}

.badge-success {
  background: #dcfce7;
  color: #166534;
  border-color: rgba(22, 101, 52, 0.20);
}

.badge-danger {
  background: #fef2f2;
  color: #991b1b;
  border-color: rgba(153, 27, 27, 0.20);
}

.badge-warning {
  background: #fef9c3;
  color: #854d0e;
  border-color: rgba(133, 77, 14, 0.20);
}

.reply-list,
.bullet-list,
.inline-actions,
.asset-list {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 12px;
}

.reply-list {
  display: grid;
}

.reply-item {
  padding: 12px 14px;
  border-radius: 16px;
  background: #f8fafc;
  border: 1px solid #e2e8f0;
}

.video-frame,
.image-preview {
  width: 100%;
  border-radius: 18px;
  margin-top: 12px;
  background: #000;
}

.room-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(320px, 0.8fr);
  gap: 18px;
  margin-top: 18px;
}

.video-stage {
  display: grid;
  gap: 14px;
}

.video-stack {
  display: grid;
  gap: 12px;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

.chat-list {
  display: grid;
  gap: 10px;
  max-height: 520px;
  overflow: auto;
  padding-right: 6px;
}

.chat-item {
  padding: 12px 14px;
  border-radius: 18px;
  background: #f8fafc;
  border: 1px solid #e2e8f0;
}

.empty-state {
  padding: 34px 18px;
  text-align: center;
  color: var(--subtle);
}

.empty-state-mark {
  width: 54px;
  height: 54px;
  margin: 0 auto 12px;
  display: grid;
  place-items: center;
  border-radius: 18px;
  background: var(--brand-light);
  border: 1px solid rgba(37, 99, 235, 0.20);
  color: var(--brand);
  font-size: 22px;
  font-weight: 700;
}

.toast-root {
  position: fixed;
  right: 18px;
  bottom: 18px;
  display: grid;
  gap: 10px;
  z-index: 9999;
}

.toast {
  min-width: 220px;
  max-width: 320px;
  padding: 14px 16px;
  border-radius: 18px;
  color: white;
  background: rgba(30, 41, 59, 0.92);
  box-shadow: var(--shadow);
  transition: opacity 0.3s ease, transform 0.3s ease;
}

.toast-success {
  background: rgba(22, 101, 52, 0.94);
  border: 2px solid rgba(255, 255, 255, 0.30);
}

.toast-error {
  background: rgba(185, 28, 28, 0.94);
  border: 2px solid rgba(255, 255, 255, 0.30);
}

.toast-hide {
  opacity: 0;
  transform: translateY(8px);
}

/* ========== 自定义确认弹窗 ========== */
.confirm-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10001;
  animation: fadeIn 0.2s;
}

.confirm-dialog {
  background: #fff;
  border-radius: 22px;
  padding: 28px 32px;
  max-width: 420px;
  width: 90%;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.2);
  animation: bounceIn 0.3s;
}

.confirm-dialog h3 {
  margin: 0 0 12px;
  font-size: 20px;
}

.confirm-dialog p {
  margin: 0 0 20px;
  color: var(--subtle);
  line-height: 1.6;
}

.confirm-actions {
  display: flex;
  justify-content: flex-end;
  gap: 12px;
}

/* ========== 骨架屏 loading ========== */
.skeleton-loading {
  background: linear-gradient(90deg, #e5e7eb 25%, #f3f4f6 50%, #e5e7eb 75%);
  background-size: 400px 100%;
  animation: skeleton-shimmer 1.5s ease-in-out infinite;
  border-radius: 12px;
}

@keyframes skeleton-shimmer {
  0% { background-position: -400px 0; }
  100% { background-position: 400px 0; }
}

.skeleton-bar {
  height: 18px;
  margin-bottom: 12px;
  border-radius: 8px;
}

.skeleton-bar-short {
  width: 40%;
}

/* ========== 网络状态横幅 ========== */
.network-banner {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  padding: 10px 16px;
  background: #fef2f2;
  color: #991b1b;
  text-align: center;
  font-size: 14px;
  font-weight: 600;
  z-index: 9998;
  border-bottom: 2px solid #fca5a5;
}

@media (max-width: 980px) {
  .auth-grid,
  .room-grid {
    grid-template-columns: 1fr;
  }

  .page-shell {
    padding: 18px 14px 40px;
  }
}

@media (max-width: 720px) {
  .form-grid,
  .stat-grid {
    grid-template-columns: 1fr;
  }

  .hero {
    padding: 22px 18px;
  }

  .top-nav {
    padding: 0 10px;
  }

  .nav-link {
    padding: 8px 10px;
    font-size: 13px;
  }
}

select {
  appearance: none;
  -webkit-appearance: none;
  -moz-appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%236b7280' d='M6 8L1 3h10z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 8px center;
  padding-right: 28px;
}

/* 媒体网格 + Lightbox */
.media-image-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
  gap: 10px;
  margin-top: 12px;
}

.media-thumbnail {
  width: 100%;
  aspect-ratio: 1;
  object-fit: cover;
  border-radius: 12px;
  cursor: pointer;
  border: 1px solid var(--line);
  transition: transform 0.15s;
}

.media-thumbnail:hover {
  transform: scale(1.05);
}

.lightbox-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.85);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10000;
  cursor: pointer;
}

.lightbox-overlay img {
  max-width: 90vw;
  max-height: 90vh;
  border-radius: 12px;
}

/* 面包屑 + 云盘网格 */
.breadcrumb {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  align-items: center;
  margin-bottom: 14px;
  font-size: 14px;
}

.breadcrumb a {
  color: var(--brand);
  cursor: pointer;
  text-decoration: none;
}

.breadcrumb span {
  color: var(--subtle);
}

.cloud-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 14px;
}

.cloud-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  padding: 18px;
  cursor: pointer;
}

.cloud-item-icon {
  font-size: 36px;
}

/* 翻转卡片 */
.flashcard-wrapper {
  perspective: 1000px;
  margin: 0 auto;
  max-width: 500px;
}

.flashcard {
  position: relative;
  min-height: 240px;
  cursor: pointer;
  transition: transform 0.6s;
  transform-style: preserve-3d;
}

.flashcard-flipped {
  transform: rotateY(180deg);
}

.flashcard-front,
.flashcard-back {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  border-radius: 22px;
  border: 1px solid var(--line);
  background: var(--paper);
  box-shadow: var(--shadow);
  padding: 28px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
}

.flashcard-back {
  transform: rotateY(180deg);
}

.flashcard-rating {
  display: flex;
  gap: 10px;
  margin-top: 18px;
  flex-wrap: wrap;
  justify-content: center;
}

.rating-btn {
  padding: 10px 18px;
  border-radius: 999px;
  border: 2px solid;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.15s;
}

.rating-btn:hover {
  transform: translateY(-1px);
}

.rating-again {
  background: #fef2f2;
  border-color: #dc2626;
  color: #dc2626;
}

.rating-hard {
  background: #fff7ed;
  border-color: #ea580c;
  color: #ea580c;
}

.rating-good {
  background: #f0fdf4;
  border-color: #16a34a;
  color: #16a34a;
}

.rating-easy {
  background: #eff6ff;
  border-color: #2563eb;
  color: #2563eb;
}

/* 答题卡 */
.answer-card-item {
  width: 100%;
  aspect-ratio: 1;
  border-radius: 6px;
  display: grid;
  place-items: center;
  font-size: 12px;
  font-weight: 600;
  cursor: default;
}
.answer-unanswered {
  background: #f1f5f9;
  color: #64748b;
  border: 1px solid #e2e8f0;
}
.answer-correct {
  background: #dcfce7;
  color: #16a34a;
  border: 1px solid #86efac;
}
.answer-wrong {
  background: #fef2f2;
  color: #dc2626;
  border: 1px solid #fca5a5;
}

/* 庆祝动画 */
.celebration-overlay {
  position: fixed;
  inset: 0;
  z-index: 2000;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: rgba(0,0,0,0.5);
  animation: fadeIn 0.3s;
}
.celebration-overlay .celebration-card {
  background: #fff;
  border-radius: 20px;
  padding: 30px 40px;
  text-align: center;
  animation: bounceIn 0.5s;
  box-shadow: 0 20px 60px rgba(0,0,0,0.2);
}
.celebration-overlay .celebration-icon {
  font-size: 64px;
  margin-bottom: 12px;
}
.celebration-overlay h2 {
  margin: 0 0 8px;
  color: var(--brand);
}
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}
@keyframes bounceIn {
  0% { transform: scale(0.3); opacity: 0; }
  50% { transform: scale(1.05); }
  70% { transform: scale(0.95); }
  100% { transform: scale(1); opacity: 1; }
}

/* ========== 通用分隔线 ========== */
.section-divider {
  margin: 28px 0;
  border: none;
  border-top: 2px solid var(--line);
}