:root {
  --color-primary: #0d7377;
  --color-secondary: #14a3a8;
  --color-accent: #17c3c8;
  --color-bg: #f5f7fa;
  --color-card: #ffffff;
  --color-text: #1a1a1a;
  --color-text-light: #5a6474;
  --color-text-muted: #8895a7;
  --color-border: #e1e5eb;
  --color-border-light: #eef1f5;
  --color-text-danger: #cf0f0f;
  --color-text-danger-hover: #bb0e0e;
}

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family:
    -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue",
    Arial, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  min-height: 100vh;
}

#app {
  min-height: 100vh;
}

/* Login page */
.login-page {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  background: var(--color-bg);
}

.login-card {
  background: var(--color-card);
  padding: 48px 56px;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
  text-align: center;
}

.login-brand {
  font-size: 32px;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 4px;
}

.login-subtitle {
  font-size: 14px;
  color: var(--color-text-muted);
  margin-bottom: 36px;
}

.login-button {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background: var(--color-primary);
  color: #fff;
  padding: 12px 32px;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 500;
  text-decoration: none;
  transition: background 0.15s ease;
}

.login-button:hover {
  background: var(--color-secondary);
}

.login-note {
  font-size: 11px;
  color: var(--color-text-muted);
  margin-top: 24px;
}

/* Header */
.header {
  background: var(--color-primary);
  padding: 14px 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 12px;
}

.header-brand {
  font-size: 16px;
  font-weight: 700;
  color: #fff;
  text-decoration: none;
}

.header-divider {
  color: rgba(255, 255, 255, 0.3);
}

.header-subtitle {
  font-size: 13px;
  color: rgba(255, 255, 255, 0.8);
}
.header-user {
  position: relative;
}

.header-avatar {
  cursor: pointer;
  background: rgba(255, 255, 255, 0.15);
  border: 1px solid rgba(255, 255, 255, 0.25);
  border-radius: 50%;
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 11px;
  font-weight: 600;
  font-family: inherit;
  transition: background 0.15s;
}

.header-avatar:hover {
  background: rgba(255, 255, 255, 0.25);
}

.header-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  min-width: 192px;
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
  overflow: hidden;
  z-index: 100;
  animation: dropdown-in 0.12s ease;
}

@keyframes dropdown-in {
  from {
    opacity: 0;
    transform: translateY(-4px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.header-dropdown-name {
  font-size: 12px;
  font-weight: 500;
  color: var(--color-text-muted);
  padding: 12px 14px;
  border-bottom: 1px solid var(--color-border-light);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.header-signout-btn {
  display: block;
  width: 100%;
  padding: 10px 14px;
  font-size: 13px;
  font-weight: 500;
  font-family: inherit;
  color: var(--color-text-danger);
  background: none;
  border: none;
  text-align: left;
  cursor: pointer;
  transition:
    background 0.12s,
    color 0.12s;
}

.header-signout-btn:hover {
  background: var(--color-bg);
  color: var(--color-text-danger-hover);
}

/* Page layout */
.page {
  max-width: 900px;
  margin: 0 auto;
  padding: 32px 24px;
}

.page-title {
  font-size: 22px;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 4px;
}

.page-subtitle {
  font-size: 13px;
  color: var(--color-text-light);
  margin-bottom: 24px;
}

/* Course grid */
.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 16px;
}

/* Course card */
.course-card {
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  overflow: hidden;
  text-decoration: none;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
  transition:
    box-shadow 0.15s ease,
    transform 0.15s ease;
}

.course-card:hover {
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
  transform: translateY(-2px);
}

.course-card-header {
  background: linear-gradient(
    135deg,
    var(--color-primary),
    var(--color-secondary)
  );
  padding: 20px;
}

.course-card-label {
  font-size: 10px;
  color: rgba(255, 255, 255, 0.7);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.course-card-label--muted {
  color: var(--color-text-muted);
}

.course-card-title {
  font-size: 17px;
  font-weight: 600;
  color: #fff;
  margin-top: 6px;
}

.course-card-body {
  padding: 16px 20px;
}

.course-card-description {
  font-size: 13px;
  color: var(--color-text-light);
  margin-bottom: 12px;
}

.course-card-counts {
  font-size: 12px;
  color: var(--color-text-muted);
}

/* Placeholder card */
.course-card--placeholder {
  border-style: dashed;
  box-shadow: none;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 180px;
  cursor: default;
}

.course-card--placeholder:hover {
  box-shadow: none;
  transform: none;
}

.course-card-placeholder-inner {
  text-align: center;
}

.course-card-placeholder-text {
  font-size: 13px;
  color: var(--color-text-muted);
  margin-top: 4px;
}

/* Breadcrumb */
.breadcrumb {
  font-size: 13px;
  color: var(--color-text-muted);
  margin-bottom: 20px;
}

.breadcrumb-link {
  color: var(--color-secondary);
  text-decoration: none;
}

.breadcrumb-link:hover {
  text-decoration: underline;
}

.breadcrumb-separator {
  margin: 0 8px;
  color: var(--color-border);
}

/* Tabs */
.tabs {
  display: flex;
  gap: 0;
  border-bottom: 2px solid var(--color-border);
  margin-bottom: 20px;
}

.tab {
  padding: 10px 20px;
  font-size: 14px;
  color: var(--color-text-muted);
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
  cursor: pointer;
  font-family: inherit;
  transition: color 0.15s ease;
}

.tab:hover {
  color: var(--color-text-light);
}

.tab--active {
  color: var(--color-primary);
  font-weight: 600;
  border-bottom-color: var(--color-primary);
}

/* Tab panels */
.tab-panel {
  display: none;
}

.tab-panel--active {
  display: block;
}

.tab-empty {
  font-size: 14px;
  color: var(--color-text-muted);
  padding: 32px 0;
  text-align: center;
}

/* Material grid */
.material-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 12px;
}

/* Material card */
.material-card {
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-left: 3px solid var(--color-secondary);
  border-radius: 8px;
  padding: 16px;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.04);
}

.material-name {
  font-size: 14px;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 4px;
}

.material-description {
  font-size: 12px;
  color: var(--color-text-light);
  margin-bottom: 10px;
}

.material-link {
  font-size: 12px;
  color: var(--color-secondary);
  text-decoration: none;
  font-weight: 500;
}

.material-link:hover {
  color: var(--color-accent);
}

.material-link--disabled {
  color: var(--color-text-muted);
}

/* Responsive */
@media (max-width: 640px) {
  .login-card {
    margin: 0 16px;
    padding: 36px 28px;
  }

  .page {
    padding: 24px 16px;
  }

  .page-title {
    font-size: 18px;
  }

  .course-grid {
    grid-template-columns: 1fr;
  }

  .material-grid {
    grid-template-columns: 1fr;
  }

  .tabs {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }

  .tab {
    padding: 10px 14px;
    font-size: 13px;
    white-space: nowrap;
  }

  .header {
    padding: 12px 16px;
  }

  .header-brand {
    font-size: 14px;
  }

  .header-subtitle {
    font-size: 11px;
  }
}