:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --accent: #f59e0b;
    --bg: #f8fafc;
    --card: #ffffff;
    --text: #0f172a;
    --muted: #64748b;
    --border: #e2e8f0;
    --radius: 12px;
    --shadow: 0 4px 24px rgba(15, 23, 42, 0.08);
}

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

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    min-height: 100vh;
}

.container {
    max-width: 980px;
    margin: 0 auto;
    padding: 0 20px 48px;
}

.site-header {
    background: linear-gradient(135deg, #1e3a8a, var(--primary));
    color: #fff;
    padding: 20px 0 28px;
    margin-bottom: 28px;
    box-shadow: var(--shadow);
}

.site-header h1 {
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: 6px;
}

.site-header p {
    opacity: 0.92;
    max-width: 640px;
}

.meta-bar {
    display: flex;
    flex-wrap: wrap;
    gap: 10px 16px;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 20px;
    font-size: 0.9rem;
    color: var(--muted);
}

.meta-bar strong {
    color: var(--text);
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 14px;
    border-radius: 8px;
    border: 1px solid var(--border);
    background: var(--card);
    color: var(--text);
    text-decoration: none;
    font-size: 0.875rem;
    cursor: pointer;
    transition: background 0.15s, border-color 0.15s;
}

.btn:hover {
    background: #f1f5f9;
}

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

.btn-primary:hover {
    background: var(--primary-dark);
}

.btn-sm {
    padding: 6px 12px;
    font-size: 0.8125rem;
}

.alert {
    padding: 12px 16px;
    border-radius: var(--radius);
    margin-bottom: 20px;
    font-size: 0.925rem;
}

.alert-warn {
    background: #fffbeb;
    border: 1px solid #fcd34d;
    color: #92400e;
}

.alert-error {
    background: #fef2f2;
    border: 1px solid #fecaca;
    color: #991b1b;
}

.lesson-table-wrap {
    background: var(--card);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    overflow: hidden;
    border: 1px solid var(--border);
}

.lesson-table {
    width: 100%;
    border-collapse: collapse;
}

.lesson-table th,
.lesson-table td {
    padding: 14px 16px;
    text-align: left;
    border-bottom: 1px solid var(--border);
    vertical-align: middle;
}

.lesson-table th {
    background: #f1f5f9;
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: var(--muted);
}

.lesson-table tr:last-child td {
    border-bottom: none;
}

.lesson-table tbody tr:hover {
    background: #f8fafc;
}

.col-no {
    width: 56px;
    text-align: center;
    font-weight: 700;
    color: var(--primary);
}

.col-note {
    font-size: 0.8125rem;
    color: var(--muted);
    white-space: nowrap;
}

.lesson-title {
    font-weight: 600;
}

.lesson-cards {
    display: none;
    gap: 12px;
}

.lesson-card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 16px;
    box-shadow: var(--shadow);
}

.lesson-card-head {
    display: flex;
    gap: 12px;
    align-items: flex-start;
    margin-bottom: 12px;
}

.lesson-card-no {
    flex-shrink: 0;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: #dbeafe;
    color: var(--primary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
}

.lesson-card-note {
    margin-top: 8px;
    font-size: 0.8125rem;
    color: var(--muted);
}

.site-footer {
    margin-top: 32px;
    text-align: center;
    font-size: 0.8125rem;
    color: var(--muted);
}

.site-footer a {
    color: var(--primary);
}

@media (max-width: 720px) {
    .lesson-table-wrap {
        display: none;
    }

    .lesson-cards {
        display: grid;
    }

    .col-note-desktop {
        display: none;
    }
}