:root {
  color-scheme: light;
  --bg: var(--aite-canvas, #f4f6f3);
  --panel: var(--aite-surface, #ffffff);
  --ink: var(--aite-ink, #17211f);
  --muted: var(--aite-muted, #64716d);
  --line: var(--aite-line, #d8ded9);
  --teal: #0f766e;
  --teal-soft: #e0f2ef;
  --gold: #b7791f;
  --rose: #b4535f;
  --shadow: var(--aite-shadow, 0 10px 28px rgba(24, 40, 35, 0.08));
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--bg);
  color: var(--ink);
  font-family: Inter, "Segoe UI", Arial, "Microsoft YaHei", sans-serif;
}

button,
input {
  font: inherit;
}

button {
  cursor: pointer;
}

.app-shell {
  display: grid;
  grid-template-columns: 260px minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  display: flex;
  flex-direction: column;
  gap: 28px;
  padding: 28px 20px;
  border-right: 1px solid var(--line);
  background: #fbfaf7;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  color: inherit;
  text-decoration: none;
}

.brand-mark {
  display: grid;
  width: 42px;
  height: 42px;
  place-items: center;
  border-radius: 8px;
  background: var(--ink);
  color: #fff;
  font-weight: 800;
}

.brand strong,
.brand small {
  display: block;
}

.brand small {
  margin-top: 2px;
  color: var(--muted);
  font-size: 12px;
}

.course-filter-nav {
  display: grid;
  gap: 8px;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: 10px;
  min-height: 42px;
  padding: 0 12px;
  border: 1px solid transparent;
  border-radius: 8px;
  background: transparent;
  color: var(--muted);
  text-align: left;
}

.nav-item:hover,
.nav-item.is-active {
  border-color: var(--line);
  background: var(--panel);
  color: var(--ink);
}

.nav-icon {
  display: grid;
  width: 22px;
  height: 22px;
  place-items: center;
  color: var(--teal);
  font-size: 14px;
}

.main {
  min-width: 0;
  padding: 32px;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}

.eyebrow {
  margin: 0 0 6px;
  color: var(--teal);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0;
  text-transform: uppercase;
}

h1 {
  margin: 0;
  font-size: clamp(30px, 4vw, 46px);
  letter-spacing: 0;
}

.ghost-button,
.primary-button,
.secondary-button {
  min-height: 42px;
  border-radius: 8px;
  border: 1px solid var(--line);
  padding: 0 16px;
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
}

.ghost-button {
  background: rgba(255, 255, 255, 0.7);
  color: var(--ink);
}

.primary-button {
  border-color: var(--ink);
  background: var(--ink);
  color: #fff;
}

.link-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  text-decoration: none;
}

.primary-button:disabled {
  cursor: wait;
  opacity: 0.72;
  transform: none;
}

.secondary-button {
  background: var(--panel);
  color: var(--ink);
}

.ghost-button:hover,
.primary-button:hover,
.secondary-button:hover {
  transform: translateY(-1px);
  box-shadow: 0 8px 18px rgba(29, 37, 35, 0.12);
}

.metric-strip {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
  margin: 28px 0 18px;
}

.metric {
  min-height: 96px;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

.metric span,
.metric small {
  display: block;
}

.metric span {
  font-size: 30px;
  font-weight: 800;
}

.metric small {
  margin-top: 4px;
  color: var(--muted);
}

.course-toolbar {
  margin: 0 0 18px;
}

.search-box {
  display: flex;
  align-items: center;
  gap: 10px;
  max-width: 420px;
  min-height: 46px;
  padding: 0 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  color: var(--muted);
}

.search-box input {
  width: 100%;
  min-width: 0;
  border: 0;
  outline: 0;
  background: transparent;
  color: var(--ink);
}

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

.course-card {
  display: grid;
  min-height: 330px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  box-shadow: var(--shadow);
  overflow: hidden;
}

.course-band {
  height: 9px;
  background: var(--course-accent, var(--teal));
}

.course-body {
  display: grid;
  gap: 18px;
  padding: 22px;
}

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

.course-title {
  min-width: 0;
}

.course-title h2 {
  margin: 0 0 5px;
  font-size: 23px;
  letter-spacing: 0;
}

.course-title p {
  margin: 0;
  color: var(--muted);
}

.status-badge {
  flex: 0 0 auto;
  border-radius: 999px;
  padding: 6px 10px;
  background: #f1eee7;
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
}

.status-badge.is-unlocked {
  background: var(--teal-soft);
  color: var(--teal);
}

.course-stats {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px;
}

.course-stat {
  min-height: 72px;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fbfaf7;
}

.course-stat strong,
.course-stat span {
  display: block;
}

.course-stat strong {
  font-size: 20px;
}

.course-stat span {
  color: var(--muted);
  font-size: 12px;
}

.invite-form {
  display: grid;
  gap: 10px;
}

.invite-row {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 10px;
}

.invite-input {
  min-width: 0;
  min-height: 42px;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 0 12px;
  color: var(--ink);
}

.invite-input:focus {
  border-color: var(--teal);
  outline: 3px solid rgba(15, 118, 110, 0.18);
}

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

.hint {
  min-height: 20px;
  margin: 0;
  color: var(--rose);
  font-size: 13px;
}

.empty-state {
  padding: 28px;
  border: 1px dashed var(--line);
  border-radius: 8px;
  color: var(--muted);
  background: rgba(255, 255, 255, 0.55);
}

.toast {
  position: fixed;
  right: 24px;
  bottom: 24px;
  max-width: min(360px, calc(100vw - 32px));
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--ink);
  color: #fff;
  box-shadow: var(--shadow);
  opacity: 0;
  transform: translateY(12px);
  pointer-events: none;
  transition: opacity 0.18s ease, transform 0.18s ease;
}

.toast.is-visible {
  opacity: 1;
  transform: translateY(0);
}

@media (max-width: 860px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: sticky;
    top: 0;
    z-index: 2;
    padding: 16px;
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }

  .course-filter-nav {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .nav-item {
    justify-content: center;
  }

  .main {
    padding: 22px 16px 36px;
  }
}

@media (max-width: 620px) {
  .topbar,
  .course-heading {
    align-items: stretch;
    flex-direction: column;
  }

  .metric-strip,
  .course-stats {
    grid-template-columns: 1fr;
  }

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

  .invite-row {
    grid-template-columns: 1fr;
  }

  .nav-item {
    padding: 0 8px;
    font-size: 14px;
  }
}