:root {
  --bg-primary: #ffffff;
  --bg-secondary: #f7f8fa;
  --bg-card: #ffffff;
  --bg-input: #f7f8fa;
  --border: #e3e6ea;
  --accent: #2952e3;
  --accent-strong: #1f3fc7;
  --accent-hover: #17309e;
  --accent-light: #2952e3;
  --accent-glow: rgba(41, 82, 227, 0.15);
  --text-primary: #14161a;
  --text-secondary: #565c66;
  --text-muted: #8b909a;
  --success: #15803d;
  --success-bg: rgba(21, 128, 61, 0.1);
  --danger: #b91c1c;
  --danger-bg: rgba(185, 28, 28, 0.08);
  --warning: #92400e;
  --warning-bg: rgba(217, 119, 6, 0.12);
  --radius: 8px;
  --radius-lg: 12px;
  --shadow: 0 1px 2px rgba(16, 24, 40, 0.04), 0 1px 3px rgba(16, 24, 40, 0.06);
}

* {
  box-sizing: border-box;
}

html {
  color-scheme: light;
}

body {
  margin: 0;
  background: var(--bg-primary);
  color: var(--text-primary);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.55;
}

a {
  color: var(--accent);
  text-decoration: none;
}
a:hover {
  text-decoration: underline;
}

.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 20px;
}

/* ---------- Nav ---------- */
.navbar {
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 20;
}
.navbar-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  max-width: 1080px;
  margin: 0 auto;
  gap: 16px;
  flex-wrap: wrap;
}
.brand {
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--text-primary);
  letter-spacing: -0.01em;
}
.brand:hover {
  text-decoration: none;
  color: var(--text-primary);
}
.nav-links {
  display: flex;
  align-items: center;
  gap: 20px;
  flex-wrap: wrap;
}
.nav-links a {
  color: var(--text-secondary);
  font-size: 0.92rem;
}
.nav-links a:hover,
.nav-links a.active {
  color: var(--text-primary);
  text-decoration: none;
}
.nav-points {
  color: var(--text-primary);
  font-weight: 600;
  font-size: 0.92rem;
}

/* ---------- Layout ---------- */
main {
  padding: 40px 0 80px;
}
.page-header {
  margin-bottom: 32px;
}
.page-header h1 {
  margin: 0 0 8px;
  font-size: 1.9rem;
  letter-spacing: -0.01em;
}
.page-header p {
  color: var(--text-secondary);
  margin: 0;
  max-width: 640px;
}

.search-bar {
  display: flex;
  gap: 10px;
  margin-bottom: 28px;
  max-width: 480px;
}
.search-bar input[type='text'] {
  flex: 1;
  background: var(--bg-primary);
  border: 1px solid var(--border);
  color: var(--text-primary);
  border-radius: var(--radius);
  padding: 10px 13px;
  font-size: 0.95rem;
  font-family: inherit;
}
.search-bar input[type='text']:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-glow);
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 18px;
  border-radius: var(--radius);
  border: 1px solid transparent;
  font-size: 0.92rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
}
.btn:hover {
  text-decoration: none;
}
.btn-primary {
  background: var(--accent-strong);
  color: #ffffff;
}
.btn-primary:hover {
  background: var(--accent-hover);
}
.btn-secondary {
  background: var(--bg-primary);
  color: var(--text-primary);
  border-color: var(--border);
}
.btn-secondary:hover {
  border-color: var(--text-secondary);
  background: var(--bg-secondary);
}
.btn-danger {
  background: var(--bg-primary);
  color: var(--danger);
  border-color: #f0c4c4;
}
.btn-danger:hover {
  background: var(--danger-bg);
}
.btn-light {
  background: var(--bg-secondary);
  color: var(--text-primary);
  border-color: var(--border);
}
.btn-light:hover {
  background: #eef0f3;
}
.btn-block {
  width: 100%;
}
.btn-sm {
  padding: 6px 14px;
  font-size: 0.85rem;
}

/* ---------- Forms ---------- */
.field {
  margin-bottom: 18px;
}
.field label {
  display: block;
  margin-bottom: 6px;
  font-size: 0.88rem;
  color: var(--text-secondary);
  font-weight: 600;
}
.field input[type='text'],
.field input[type='email'],
.field input[type='password'],
.field input[type='number'],
.field input[type='url'],
.field textarea,
.field select {
  width: 100%;
  background: var(--bg-primary);
  border: 1px solid var(--border);
  color: var(--text-primary);
  border-radius: var(--radius);
  padding: 10px 13px;
  font-size: 0.95rem;
  font-family: inherit;
}
.field input:focus,
.field textarea:focus,
.field select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-glow);
}
.field textarea {
  resize: vertical;
  min-height: 90px;
}
.field-hint {
  color: var(--text-muted);
  font-size: 0.82rem;
  margin-top: 4px;
}
.checkbox-row {
  display: flex;
  align-items: center;
  gap: 8px;
}
.checkbox-row label {
  margin: 0;
  font-weight: 500;
  color: var(--text-primary);
}

.auth-card {
  max-width: 420px;
  margin: 20px auto;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
  box-shadow: var(--shadow);
}
.auth-card h1 {
  margin-top: 0;
  font-size: 1.4rem;
}
.auth-switch {
  margin-top: 18px;
  text-align: center;
  color: var(--text-secondary);
  font-size: 0.9rem;
}

/* ---------- Flash messages ---------- */
.flash {
  padding: 12px 16px;
  border-radius: var(--radius);
  margin-bottom: 16px;
  font-size: 0.9rem;
  border: 1px solid transparent;
}
.flash-success {
  background: var(--success-bg);
  color: var(--success);
  border-color: rgba(21, 128, 61, 0.25);
}
.flash-error {
  background: var(--danger-bg);
  color: var(--danger);
  border-color: rgba(185, 28, 28, 0.25);
}

/* ---------- Cards / grid ---------- */
.lesson-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
}
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  box-shadow: var(--shadow);
}
.card-thumb {
  aspect-ratio: 16 / 9;
  background: var(--bg-secondary);
  position: relative;
}
.card-thumb img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}
.card-body {
  padding: 18px 20px 22px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  flex: 1;
}
.card-body h3 {
  margin: 0;
  font-size: 1.08rem;
}
.card-desc {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin: 0;
  flex: 1;
}
.card-meta {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.85rem;
  color: var(--text-muted);
}
.status-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 10px;
  border-radius: var(--radius);
  font-size: 0.76rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}
.status-passed {
  background: var(--success-bg);
  color: var(--success);
}
.status-locked {
  background: var(--bg-secondary);
  color: var(--text-muted);
}

/* ---------- Video embed ---------- */
.video-embed {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  background: #000;
  border-radius: var(--radius-lg);
  overflow: hidden;
  margin-bottom: 24px;
}
.video-embed iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

/* ---------- Badges ---------- */
.badge {
  display: inline-flex;
  align-items: center;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent-strong);
  border-radius: var(--radius);
  padding: 12px 16px;
}
.badge-name {
  font-weight: 700;
}
.badge-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 14px;
  margin-top: 12px;
}

/* ---------- Exercise ---------- */
.question-block {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 22px 24px;
  margin-bottom: 18px;
}
.question-block h3 {
  margin-top: 0;
  font-size: 1.02rem;
}
.option-row {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border-radius: var(--radius);
  border: 1px solid transparent;
}
.option-row:hover {
  background: var(--bg-secondary);
}
.option-row label {
  cursor: pointer;
  flex: 1;
  color: var(--text-primary);
}
.option-row input {
  accent-color: var(--accent-strong);
  width: 17px;
  height: 17px;
}

.result-hero {
  text-align: center;
  padding: 48px 24px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
}
.result-status {
  display: inline-block;
  padding: 5px 14px;
  border-radius: var(--radius);
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: 16px;
}
.result-status-pass {
  background: var(--success-bg);
  color: var(--success);
}
.result-status-fail {
  background: var(--warning-bg);
  color: var(--warning);
}
.result-score {
  font-size: 2.2rem;
  font-weight: 800;
  margin: 6px 0;
}

/* ---------- Leaderboard ---------- */
.leaderboard-table {
  width: 100%;
  border-collapse: collapse;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}
.leaderboard-table th,
.leaderboard-table td {
  padding: 14px 18px;
  text-align: left;
  border-bottom: 1px solid var(--border);
  font-size: 0.93rem;
}
.leaderboard-table th {
  background: var(--bg-secondary);
  color: var(--text-muted);
  font-size: 0.76rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.leaderboard-table tr:last-child td {
  border-bottom: none;
}
.leaderboard-table tr.current-user {
  background: var(--accent-glow);
}
.rank-cell {
  font-weight: 700;
  color: var(--text-primary);
  width: 60px;
}

/* ---------- Admin ---------- */
.admin-table {
  width: 100%;
  border-collapse: collapse;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}
.admin-table th,
.admin-table td {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border);
  text-align: left;
  font-size: 0.9rem;
  vertical-align: middle;
}
.admin-table th {
  background: var(--bg-secondary);
  color: var(--text-muted);
  font-size: 0.76rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.admin-table tr:last-child td {
  border-bottom: none;
}
.row-actions {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}
.section {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  margin-bottom: 24px;
  box-shadow: var(--shadow);
}
.section h2 {
  margin-top: 0;
  font-size: 1.1rem;
}
.option-input-row {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 10px;
}
.option-input-row input[type='text'] {
  flex: 1;
}
.two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}
.inline-form {
  display: inline;
}
.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--text-muted);
}
.empty-state h2 {
  color: var(--text-primary);
}

.tag {
  display: inline-block;
  padding: 3px 10px;
  border-radius: var(--radius);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}
.tag-published {
  background: var(--success-bg);
  color: var(--success);
}
.tag-draft {
  background: var(--warning-bg);
  color: var(--warning);
}

.site-footer {
  margin-top: 50px;
  height: 100px;
  padding-top: 50px;
  background: var(--bg-primary);
  border-top: 1px solid var(--border);
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
}

@media (max-width: 640px) {
  .two-col {
    grid-template-columns: 1fr;
  }
  .navbar-inner {
    gap: 10px;
  }
  .page-header h1 {
    font-size: 1.5rem;
  }
}