/* 首页 Hero */
.hero {
  position: relative;
  padding: 5rem 0 4rem;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  inset: -20% -10% auto;
  height: 70%;
  background:
    radial-gradient(
      ellipse at 30% 20%,
      rgba(100, 149, 237, 0.25),
      transparent 60%
    ),
    radial-gradient(
      ellipse at 80% 40%,
      rgba(143, 180, 245, 0.2),
      transparent 50%
    );
  pointer-events: none;
}

.hero-content {
  position: relative;
  max-width: 640px;
}

.hero-eyebrow {
  display: inline-block;
  margin-bottom: 1rem;
  padding: 0.35rem 0.9rem;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--color-primary-darker);
  background: var(--color-primary-pale);
  border-radius: var(--radius-full);
}

.hero h1 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 700;
  letter-spacing: -0.02em;
}

.hero h1 span {
  background: linear-gradient(
    135deg,
    var(--color-primary-dark),
    var(--color-primary)
  );
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-desc {
  font-size: 1.15rem;
  color: var(--color-text-secondary);
  margin: 1.25rem 0 2rem;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.features {
  padding: 4rem 0;
}

.section-title {
  text-align: center;
  margin-bottom: 2.5rem;
}

.section-title h2 {
  font-size: 1.75rem;
}

.section-title p {
  color: var(--color-text-secondary);
  margin: 0.5rem 0 0;
}

.feature-card {
  text-align: center;
  padding: 2rem 1.5rem;
}

.feature-icon {
  width: 56px;
  height: 56px;
  margin: 0 auto 1rem;
  display: grid;
  place-items: center;
  font-size: 1.5rem;
  background: var(--color-primary-pale);
  color: var(--color-primary-dark);
  border-radius: var(--radius-md);
}

/* 认证页 */
.auth-page {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 2rem 1rem;
  background: linear-gradient(
    160deg,
    var(--color-bg) 0%,
    var(--color-primary-pale) 100%
  );
}

.auth-card {
  width: min(100%, 420px);
  padding: 2.5rem;
}

.auth-card h1 {
  font-size: 1.5rem;
  text-align: center;
  margin-bottom: 0.25rem;
}

.auth-subtitle {
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.95rem;
  margin-bottom: 2rem;
}

.auth-footer {
  margin-top: 1.5rem;
  text-align: center;
  font-size: 0.9rem;
  color: var(--color-text-secondary);
}

/* 仪表盘 */
.dashboard-welcome {
  margin-bottom: 2rem;
}

.dashboard-welcome h1 {
  font-size: 1.75rem;
}

.stat-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  margin-bottom: 2rem;
}

.stat-card {
  padding: 1.25rem;
}

.stat-card .value {
  font-size: 2rem;
  font-weight: 700;
  color: var(--color-primary-dark);
}

.stat-card .label {
  font-size: 0.9rem;
  color: var(--color-text-muted);
}

/* 管理后台 */
.admin-header {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.admin-header h1 {
  font-size: 1.75rem;
  margin: 0 0 0.25rem;
}

.admin-subtitle {
  margin: 0;
  color: var(--color-text-secondary);
  font-size: 0.95rem;
}

.admin-toolbar {
  padding: 1rem 1.25rem;
  margin-bottom: 1rem;
}

.admin-search {
  max-width: 360px;
}

.admin-table-wrap {
  padding: 0;
  overflow: hidden;
}

.admin-table-scroll {
  overflow-x: auto;
}

.admin-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
}

.admin-table th,
.admin-table td {
  padding: 0.65rem 1rem;
  text-align: left;
  border-bottom: 1px solid var(--color-border);
  vertical-align: middle;
}

.admin-table th {
  font-weight: 600;
  color: var(--color-text-secondary);
  background: var(--color-bg-subtle, rgba(100, 149, 237, 0.06));
  white-space: nowrap;
}

.admin-table tbody tr:hover {
  background: rgba(100, 149, 237, 0.04);
}

.admin-empty {
  text-align: center;
  color: var(--color-text-muted);
  padding: 2rem 1rem !important;
}

.admin-actions {
  white-space: nowrap;
}

.admin-actions .btn-sm {
  padding: 0.2rem 0.45rem;
  font-size: 0.78rem;
}

.admin-btn-danger {
  color: #b42318;
}

.admin-btn-danger:hover {
  color: #912018;
  background: rgba(180, 35, 24, 0.08);
}

.admin-badge {
  display: inline-block;
  margin-right: 0.25rem;
  padding: 0.1rem 0.4rem;
  border-radius: 4px;
  font-size: 0.72rem;
  font-weight: 500;
}

.admin-badge--ok {
  background: rgba(34, 139, 34, 0.12);
  color: #1a6b1a;
}

.admin-badge--off {
  background: rgba(120, 120, 120, 0.15);
  color: var(--color-text-muted);
}

.admin-badge--admin {
  background: var(--color-primary-pale);
  color: var(--color-primary-darker);
}

.admin-msg {
  margin: 0;
  padding: 0.75rem 1rem;
  font-size: 0.9rem;
  color: var(--color-primary-dark);
  border-bottom: 1px solid var(--color-border);
}

.admin-msg--error {
  color: #b42318;
}

.admin-dialog {
  border: none;
  border-radius: var(--radius-lg, 12px);
  padding: 0;
  max-width: 420px;
  width: calc(100% - 2rem);
  box-shadow: var(--shadow-lg, 0 12px 40px rgba(0, 0, 0, 0.15));
}

.admin-dialog::backdrop {
  background: rgba(15, 23, 42, 0.35);
}

.admin-dialog-form {
  padding: 1.5rem;
}

.admin-dialog-form h2 {
  margin: 0 0 1rem;
  font-size: 1.2rem;
}

.admin-dialog-form .form-label {
  display: block;
  margin: 0.75rem 0 0.35rem;
  font-size: 0.85rem;
  color: var(--color-text-secondary);
}

.admin-dialog-form .form-input {
  width: 100%;
}

.admin-check {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-top: 0.75rem;
  font-size: 0.9rem;
  cursor: pointer;
}

.admin-dialog-actions {
  display: flex;
  justify-content: flex-end;
  gap: 0.5rem;
  margin-top: 1.25rem;
}

/* 课程目录 · 页头 */
.courses-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 1.25rem;
}

.courses-head h1 {
  margin: 0;
  font-size: 1.6rem;
  font-weight: 600;
}

.courses-head-note {
  margin: 0;
  font-size: 0.85rem;
  color: var(--color-text-muted);
  font-variant-numeric: tabular-nums;
}

/* 课程目录 · 筛选：文字标签页样式，不用胶囊按钮 */
.course-toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem 2.25rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--color-border);
}

.course-filter-row {
  display: flex;
  align-items: baseline;
  gap: 0.85rem;
  min-width: 0;
}

.course-filter-label {
  flex: 0 0 auto;
  white-space: nowrap;
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
}

.course-filter-group {
  display: flex;
  flex-wrap: wrap;
  gap: 1.1rem;
  min-width: 0;
}

.course-filter-btn {
  padding: 0.1rem 0 0.2rem;
  font-family: inherit;
  font-size: 0.86rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  background: none;
  border: none;
  border-bottom: 1.5px solid transparent;
  cursor: pointer;
  transition:
    color var(--transition),
    border-color var(--transition);
}

.course-filter-btn:hover {
  color: var(--color-primary-dark);
}

.course-filter-btn.active {
  color: var(--color-primary-darker);
  font-weight: 600;
  border-bottom-color: var(--color-primary);
}

.course-filter-hint {
  flex-basis: 100%;
  margin: 0.2rem 0 0;
  font-size: 0.82rem;
  color: var(--color-text-muted);
}

/* 课程目录 · 列表：一行一门课，用分隔线组织 */
.course-row {
  display: grid;
  grid-template-columns: 2.5rem minmax(0, 1fr) auto 1.5rem;
  grid-template-areas: "index main meta arrow";
  align-items: start;
  gap: 0 1.25rem;
  padding: 1.35rem 0.75rem 1.35rem 0.25rem;
  border-bottom: 1px solid var(--color-border);
  color: inherit;
  text-decoration: none;
  transition: background var(--transition);
}

.course-row:hover {
  background: var(--color-primary-pale);
}

.course-row-index {
  grid-area: index;
  padding-top: 0.2rem;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-variant-numeric: tabular-nums;
  color: var(--color-text-muted);
}

.course-row-main {
  grid-area: main;
  min-width: 0;
}

.course-row-title {
  display: block;
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--color-text);
}

.course-row-desc {
  display: block;
  margin-top: 0.4rem;
  font-size: 0.875rem;
  line-height: 1.65;
  color: var(--color-text-secondary);
}

.course-row-meta {
  grid-area: meta;
  padding-top: 0.25rem;
  font-size: 0.8rem;
  color: var(--color-text-muted);
  text-align: right;
  white-space: nowrap;
}

.course-row-arrow {
  grid-area: arrow;
  align-self: start;
  padding-top: 0.3rem;
  font-size: 0.9rem;
  color: var(--color-text-muted);
  transition:
    transform var(--transition),
    color var(--transition);
}

.course-row:hover .course-row-arrow {
  color: var(--color-primary-dark);
  transform: translateX(3px);
}

@media (max-width: 720px) {
  .course-row {
    grid-template-columns: 1.75rem minmax(0, 1fr) 1.25rem;
    grid-template-areas:
      "index main arrow"
      "index meta meta";
    gap: 0.45rem 0.85rem;
    padding: 1.1rem 0.25rem 1.1rem 0;
  }

  .course-row-meta {
    padding-top: 0;
    text-align: left;
    white-space: normal;
  }

  .course-row-arrow {
    align-self: start;
    padding-top: 0.3rem;
  }

  .course-toolbar {
    gap: 0.6rem 1.5rem;
  }
}

/* 学习页布局：左栏课时 | 中间正文+右索引 */
.learn-layout {
  display: block;
  gap: 0;
  min-height: calc(100vh - var(--header-height));
  margin-top: var(--header-height);
}

.learn-center {
  position: relative;
  min-width: 0;
  margin-left: var(--sidebar-width);
}

.learn-sidebar {
  position: fixed;
  left: 0;
  top: var(--header-height);
  width: var(--sidebar-width);
  height: calc(100vh - var(--header-height));
  overflow-y: auto;
  padding: 1.5rem;
  background: var(--color-bg-elevated);
  border-right: 1px solid var(--color-border);
  contain: layout style;
}

.learn-sidebar-head {
  margin-bottom: 1.5rem;
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--color-border);
}

.learn-course-row {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 0.35rem 0.5rem;
  margin-bottom: 0.75rem;
}

.learn-sidebar-label--inline {
  margin: 0;
  flex-shrink: 0;
}

.learn-course-row .learn-course-title {
  margin: 0;
  flex: 1;
  min-width: 0;
}

.learn-back-link {
  width: 100%;
}

.learn-sidebar-label {
  margin: 0 0 0.35rem;
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-text-muted);
}

.learn-sidebar-label--lessons {
  margin-bottom: 0.65rem;
}

.learn-course-title {
  margin: 0;
  font-size: 1.05rem;
  font-weight: 600;
  line-height: 1.4;
  color: var(--color-text);
}

.lesson-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.lesson-list li {
  margin-bottom: 2px;
}

.lesson-list li .lesson-nav-item {
  display: flex;
  align-items: flex-start;
  gap: 0.7rem;
  width: 100%;
  padding: 0.75rem 0.85rem 0.75rem 0.65rem;
  border: none;
  border-left: 3px solid transparent;
  border-radius: 0;
  background: transparent;
  font-family: inherit;
  font-size: 0.88rem;
  line-height: 1.45;
  text-align: left;
  color: var(--color-text-secondary);
  cursor: pointer;
  appearance: none;
  -webkit-appearance: none;
  transition:
    background 0.18s ease,
    color 0.18s ease,
    border-color 0.18s ease;
}

.lesson-list li .lesson-nav-item:focus {
  outline: none;
}

.lesson-list li .lesson-nav-item:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 1px;
}

.lesson-list li .lesson-nav-item:hover {
  background: var(--color-primary-ghost);
  color: var(--color-primary-dark);
}

.lesson-list li .lesson-nav-item:hover .lesson-nav-index {
  color: var(--color-primary-dark);
}

.lesson-list li .lesson-nav-item.active {
  background: var(--color-primary-pale);
  color: var(--color-primary-darker);
  border-left-color: var(--color-primary);
}

.lesson-list li .lesson-nav-item.active .lesson-nav-index {
  color: var(--color-primary-darker);
}

.lesson-list li .lesson-nav-item.active .lesson-nav-text {
  font-weight: 500;
}

.lesson-nav-index {
  flex-shrink: 0;
  min-width: 1.35rem;
  font-size: 0.72rem;
  font-weight: 600;
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.04em;
  color: var(--color-text-muted);
  padding-top: 0.12em;
}

.lesson-nav-text {
  flex: 1;
  min-width: 0;
}

.lesson-list li .lesson-nav-item.done .lesson-nav-text::after {
  content: "✓";
  display: inline-block;
  margin-left: 0.45rem;
  font-size: 0.8em;
  font-weight: 600;
  color: var(--color-success);
  vertical-align: 0.05em;
}

.learn-main {
  padding: 2rem 2.5rem 4rem;
  min-width: 0;
  width: 100%;
  max-width: calc(100vw - var(--sidebar-width) - 2rem);
  box-sizing: border-box;
}

/* 右上角固定小字目录（不随正文流到底部） */
.learn-toc {
  position: fixed;
  top: calc(var(--header-height) + 1rem);
  right: 1.25rem;
  z-index: 50;
  width: 10.5rem;
  max-height: calc(100vh - var(--header-height) - 1.75rem);
  overflow-x: hidden;
  overflow-y: auto;
  padding: 0;
  background: transparent;
  border: none;
  pointer-events: auto;
}

.learn-toc .learn-sidebar-label {
  margin: 0 0 0.5rem;
  font-size: 0.62rem;
  letter-spacing: 0.16em;
}

.lesson-toc-nav {
  display: flex;
  flex-direction: column;
  gap: 0.05rem;
}

.lesson-toc-empty {
  margin: 0;
  font-size: 0.72rem;
  color: var(--color-text-muted);
  line-height: 1.45;
}

.lesson-toc-link {
  display: block;
  width: 100%;
  padding: 0.18rem 0;
  border: none;
  border-radius: 0;
  background: transparent;
  font-family: inherit;
  font-size: 0.72rem;
  line-height: 1.4;
  text-align: left;
  color: var(--color-text-muted);
  cursor: pointer;
  appearance: none;
  -webkit-appearance: none;
  transition: color 0.15s ease;
}

.lesson-toc-link:hover {
  color: var(--color-primary-dark);
}

.lesson-toc-link:focus {
  outline: none;
}

.lesson-toc-link:focus-visible {
  outline: 1px solid var(--color-primary);
  outline-offset: 2px;
}

.lesson-toc-link.active {
  color: var(--color-primary-darker);
  font-weight: 600;
}

.lesson-toc-link--h2 {
  font-size: 0.74rem;
  font-weight: 600;
  color: var(--color-text-secondary);
}

.lesson-toc-link--h3 {
  padding-left: 0.55rem;
  font-size: 0.68rem;
  font-weight: 400;
}

@media (min-width: 1100px) {
  .learn-main {
    /* 左侧栏与右侧固定索引之间尽量铺满 */
    max-width: calc(100vw - var(--sidebar-width) - 12.5rem);
    padding-right: 2rem;
  }
}

.math-content.is-loading {
  opacity: 0.45;
  pointer-events: none;
  transition: opacity 0.12s ease;
}

.lesson-header {
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--color-border);
}

.lesson-header h1 {
  font-size: 1.5rem;
}

.learn-actions {
  margin-top: 2rem;
  display: flex;
  gap: 0.75rem;
}

@media (max-width: 1099px) {
  .learn-toc {
    display: none;
  }

  .learn-main {
    padding-right: 2.5rem;
  }
}

@media (max-width: 900px) {
  .learn-layout {
    grid-template-columns: 1fr;
  }

  .learn-sidebar {
    position: relative;
    left: auto;
    top: 0;
    width: auto;
    height: auto;
    max-height: none;
    border-right: none;
    border-bottom: 1px solid var(--color-border);
  }

  .learn-center {
    margin-left: 0;
  }

  .learn-main {
    max-width: none;
    padding: 1.5rem 1rem 3rem;
  }
}