:root {
  --brand: #4f46e5;
}
body { font-family: 'Segoe UI', system-ui, sans-serif; background:#f7f8fb; }
[data-bs-theme="dark"] body { background:#0f1117; }
.navbar-brand i { color: var(--brand); }
.btn-primary { background-color: var(--brand); border-color: var(--brand); }
.btn-primary:hover { background-color:#4338ca; border-color:#4338ca; }
.text-primary { color: var(--brand) !important; }
.hero { padding: 5rem 0 4rem; }
.card-course { border:none; border-radius: 1rem; box-shadow: 0 4px 20px rgba(0,0,0,.06); transition:.2s transform; height:100%; }
.card-course:hover { transform: translateY(-4px); }
.badge-level { font-size:.7rem; letter-spacing:.05em; }
.progress { height: 10px; border-radius: 10px; }
.sidebar-lessons .list-group-item.active { background: var(--brand); border-color: var(--brand); }
.lesson-content img { max-width:100%; border-radius:.5rem; }
.prompt-card pre { white-space: pre-wrap; background:#f1f2f6; padding:.75rem; border-radius:.5rem; font-size:.85rem; }
[data-bs-theme="dark"] .prompt-card pre { background:#1a1d27; }
.cert-box { border:6px double var(--brand); padding:3rem; text-align:center; background:#fff; }