```css
body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

.tabs-container .nav-tabs {
    padding-left: 20px;
    border-bottom: none;
}

.tabs-container .nav-link {
    border: none;
    border-radius: 0;
    color: #495057;
    position: relative;
}

.tabs-container .nav-link.active {
    color: #0d6efd;
    background-color: transparent;
    border-bottom: 2px solid #0d6efd;
}

.list-group-item {
    border-left: none;
    border-right: none;
    cursor: pointer;
}

.list-group-item.active {
    background-color: #e7f1ff;
    color: #0d6efd;
    border-color: rgba(0,0,0,.125);
}

.section-header, .notes-header {
    background-color: #f8f9fa;
}

iframe {
    min-height: 100%;
}
```