/* ================================================================
   Linda's English Hub — 可复用组件样式
   
   覆盖：按钮、卡片、徽章、进度条、标签、导航、提示框、表单
   所有颜色使用 CSS 变量，不写死十六进制值
   ================================================================ */

/* ================================================================
   1. 按钮 (Button)
   ================================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: 0.625rem 1.5rem;
  font-size: var(--text-base);
  font-weight: var(--weight-semibold);
  line-height: 1.4;
  border-radius: var(--radius-md);
  border: 2px solid transparent;
  transition: all var(--transition-fast);
  white-space: nowrap;
  user-select: none;
}
.btn:active {
  transform: scale(0.97);
}
.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

/* 主按钮 */
.btn-primary {
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  color: var(--color-text-white);
  border-color: transparent;
}
.btn-primary:hover {
  box-shadow: 0 4px 15px rgba(212, 83, 126, 0.35);
  transform: translateY(-1px);
  color: var(--color-text-white);
}
.btn-primary:active {
  transform: translateY(0);
}

/* 次要按钮 */
.btn-secondary {
  background: var(--color-surface);
  color: var(--color-primary);
  border-color: var(--color-primary);
}
.btn-secondary:hover {
  background: var(--color-primary-light);
  border-color: var(--color-primary-dark);
  color: var(--color-primary-dark);
}

/* 轮廓按钮 */
.btn-outline {
  background: transparent;
  color: var(--color-text-white);
  border-color: rgba(255,255,255,0.5);
}
.btn-outline:hover {
  background: rgba(255,255,255,0.15);
  border-color: var(--color-text-white);
  color: var(--color-text-white);
}

/* 小尺寸 */
.btn-sm {
  padding: 0.375rem 1rem;
  font-size: var(--text-sm);
}

/* 大尺寸 */
.btn-lg {
  padding: 0.875rem 2rem;
  font-size: var(--text-lg);
}

/* 图标按钮 */
.btn-icon {
  padding: 0.5rem;
  border-radius: var(--radius-full);
  width: 40px;
  height: 40px;
}

/* ================================================================
   2. 卡片 (Card)
   ================================================================ */
.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border-light);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-base);
}
.card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-3px);
}

/* 点击型卡片 */
.card-clickable {
  cursor: pointer;
  text-decoration: none;
  color: inherit;
}
.card-clickable:hover {
  border-color: var(--color-primary);
}

/* 卡片内分区 */
.card-header {
  margin-bottom: var(--spacing-md);
}
.card-footer {
  margin-top: var(--spacing-md);
  padding-top: var(--spacing-md);
  border-top: 1px solid var(--color-border-light);
}

/* 功能导航卡片（首页专用）*/
.feature-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  padding: var(--spacing-xl) var(--spacing-lg);
}
.feature-card .card-icon {
  font-size: 2.5rem;
  margin-bottom: var(--spacing-md);
  width: 72px;
  height: 72px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-primary-xlight);
  border-radius: var(--radius-xl);
  color: var(--color-primary);
  transition: all var(--transition-base);
}
.feature-card:hover .card-icon {
  background: var(--color-primary);
  color: var(--color-text-white);
  transform: scale(1.05);
}
.feature-card .card-title {
  font-size: var(--text-lg);
  font-weight: var(--weight-semibold);
  color: var(--color-text-main);
  margin-bottom: var(--spacing-xs);
}
.feature-card .card-desc {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  line-height: var(--leading-relaxed);
}

/* 数据卡片（数字统计）*/
.stat-card {
  text-align: center;
  padding: var(--spacing-lg);
}
.stat-card .stat-value {
  font-size: var(--text-4xl);
  font-weight: var(--weight-extrabold);
  color: var(--color-primary);
  line-height: 1.1;
}
.stat-card .stat-label {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
  margin-top: var(--spacing-xs);
}

/* ================================================================
   3. 徽章/标签 (Badge / Tag)
   ================================================================ */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 0.15em 0.6em;
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  border-radius: var(--radius-full);
  line-height: 1.6;
}

.badge-primary {
  background: var(--color-primary-light);
  color: var(--color-primary-dark);
}
.badge-success {
  background: var(--color-success-light);
  color: var(--color-success);
}
.badge-warning {
  background: var(--color-warning-light);
  color: var(--color-warning);
}
.badge-error {
  background: var(--color-error-light);
  color: var(--color-error);
}
.badge-info {
  background: var(--color-info-light);
  color: var(--color-info);
}

/* 标签（词性/难度）*/
.tag {
  display: inline-flex;
  align-items: center;
  padding: 0.125rem 0.5rem;
  font-size: var(--text-xs);
  font-weight: var(--weight-medium);
  border-radius: var(--radius-sm);
  background: var(--color-primary-xlight);
  color: var(--color-primary-dark);
  border: 1px solid var(--color-border);
}

/* ================================================================
   4. 进度条 (Progress Bar)
   ================================================================ */
.progress-bar {
  width: 100%;
  height: 8px;
  background: var(--color-primary-xlight);
  border-radius: var(--radius-full);
  overflow: hidden;
}
.progress-bar .progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--color-primary), var(--color-primary-dark));
  border-radius: var(--radius-full);
  transition: width 0.6s ease;
}

/* 带文字的进度条 */
.progress-stats {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--spacing-sm);
}
.progress-stats .progress-label {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
}
.progress-stats .progress-value {
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  color: var(--color-primary-dark);
}

/* ================================================================
   5. 提示框 (Alert)
   ================================================================ */
.alert {
  display: flex;
  align-items: flex-start;
  gap: var(--spacing-sm);
  padding: var(--spacing-md) var(--spacing-lg);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
  border: 1px solid transparent;
}

.alert-success {
  background: var(--color-success-light);
  border-color: var(--color-success);
  color: #1a6b4a;
}
.alert-error {
  background: var(--color-error-light);
  border-color: var(--color-error);
  color: #a82020;
}
.alert-info {
  background: var(--color-info-light);
  border-color: var(--color-info);
  color: #2c5fa1;
}
.alert-warning {
  background: var(--color-warning-light);
  border-color: var(--color-warning);
  color: #a06014;
}

.alert .alert-icon {
  flex-shrink: 0;
  font-size: var(--text-lg);
}

/* ================================================================
   6. 导航标签页 (Nav Tabs)
   ================================================================ */
.nav-tabs {
  display: flex;
  gap: 0;
  border-bottom: 2px solid var(--color-border-light);
  margin-bottom: var(--spacing-lg);
}
.nav-tab {
  padding: var(--spacing-sm) var(--spacing-lg);
  font-size: var(--text-base);
  font-weight: var(--weight-medium);
  color: var(--color-text-secondary);
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
  transition: all var(--transition-fast);
  cursor: pointer;
}
.nav-tab:hover {
  color: var(--color-primary);
}
.nav-tab.active {
  color: var(--color-primary);
  font-weight: var(--weight-semibold);
  border-bottom-color: var(--color-primary);
}

/* 响应式滚动 */
@media (max-width: 767px) {
  .nav-tabs {
    overflow-x: auto;
    flex-wrap: nowrap;
    -webkit-overflow-scrolling: touch;
  }
  .nav-tab {
    white-space: nowrap;
    padding: var(--spacing-sm) var(--spacing-md);
  }
}

/* ================================================================
   7. 表单元素
   ================================================================ */
.form-group {
  margin-bottom: var(--spacing-md);
}

.form-label {
  display: block;
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
  color: var(--color-text-main);
  margin-bottom: var(--spacing-xs);
}

.form-input {
  width: 100%;
  padding: 0.625rem 0.875rem;
  font-size: var(--text-base);
  color: var(--color-text-main);
  background: var(--color-surface);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-md);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  outline: none;
}

.form-input:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(212, 83, 126, 0.12);
}

.form-input::placeholder {
  color: var(--color-text-muted);
}

select.form-input {
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%236B3950' stroke-width='2'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.75rem center;
  padding-right: 2.5rem;
}

/* ================================================================
   8. 空状态
   ================================================================ */
.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: var(--spacing-3xl) var(--spacing-lg);
  text-align: center;
}

.empty-state .empty-icon {
  font-size: 3rem;
  color: var(--color-text-muted);
  margin-bottom: var(--spacing-md);
}

.empty-state .empty-title {
  font-size: var(--text-lg);
  font-weight: var(--weight-semibold);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-xs);
}

.empty-state .empty-desc {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  max-width: 360px;
}

/* ================================================================
   9. 搜索框
   ================================================================ */
.search-box {
  position: relative;
  max-width: 400px;
}
.search-box .form-input {
  padding-left: 2.5rem;
}
.search-box .search-icon {
  position: absolute;
  left: 0.875rem;
  top: 50%;
  transform: translateY(-50%);
  color: var(--color-text-muted);
  font-size: var(--text-base);
}

/* ================================================================
   10. 顶部导航栏 (Site Header) — 全站统一
   ================================================================ */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border-light);
  z-index: var(--z-sticky);
  display: flex;
  align-items: center;
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--color-primary-dark);
  font-weight: var(--weight-bold);
  font-size: var(--text-xl);
  text-decoration: none;
}

.logo i {
  font-size: 1.6rem;
  color: var(--color-primary);
}

/* 桌面导航 */
.nav-links {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.nav-links a {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.5rem 0.875rem;
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
  color: var(--color-text-secondary);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  text-decoration: none;
}

.nav-links a i { font-size: 0.9rem; }

.nav-links a:hover {
  color: var(--color-primary);
  background: var(--color-primary-xlight);
}

.nav-links a.active {
  color: var(--color-primary);
  background: var(--color-primary-light);
  font-weight: var(--weight-semibold);
}

/* 汉堡菜单按钮 */
.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: 0.5rem;
  background: none;
  border: none;
  cursor: pointer;
}

.menu-toggle span {
  display: block;
  width: 22px;
  height: 2.5px;
  background: var(--color-text-main);
  border-radius: 2px;
  transition: all var(--transition-fast);
}

@media (max-width: 767px) {
  .menu-toggle { display: flex; }

  .nav-links {
    display: none;
    position: absolute;
    top: var(--header-height);
    left: 0;
    right: 0;
    flex-direction: column;
    background: var(--color-surface);
    border-bottom: 2px solid var(--color-border-light);
    box-shadow: var(--shadow-lg);
    padding: var(--spacing-sm);
    gap: 0;
  }

  .nav-links.open { display: flex; }

  .nav-links a {
    padding: 0.75rem 1rem;
    border-radius: var(--radius-md);
    width: 100%;
  }
}

/* ================================================================
   11. 全站页脚 (Site Footer) — 深色底、与首页一致
   ================================================================ */
.site-footer {
  background: var(--color-text-main);
  color: rgba(255, 255, 255, 0.7);
  padding: var(--spacing-2xl) 0;
  text-align: center;
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
  margin-top: var(--spacing-2xl);
}

.site-footer a {
  color: rgba(255, 255, 255, 0.8);
  text-decoration: none;
}

.site-footer a:hover {
  color: var(--color-text-white);
}

.site-footer .footer-brand {
  color: var(--color-text-white);
  font-weight: var(--weight-bold);
  font-size: var(--text-lg);
  margin-bottom: var(--spacing-sm);
}

.site-footer .beian {
  margin-top: var(--spacing-md);
  font-size: var(--text-xs);
  color: rgba(255, 255, 255, 0.5);
}

.site-footer .beian a {
  color: rgba(255, 255, 255, 0.5);
}

/* ================================================================
   12. 子页面 Hero（通用渐变横幅）
   ================================================================ */
.page-hero {
  background: linear-gradient(135deg, #D4537E, #993556);
  padding: var(--spacing-2xl) 0;
  text-align: center;
  color: white;
}

.page-hero h1 {
  font-size: var(--text-3xl);
  font-weight: var(--weight-bold);
  margin-bottom: var(--spacing-xs);
}

.page-hero p {
  opacity: 0.85;
  font-size: var(--text-md);
}

/* ================================================================
   13. 翻页按钮（上/下一题）
   ================================================================ */
.page-nav {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: var(--spacing-md);
  margin-top: var(--spacing-xl);
}

.page-counter {
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
}