body {
    font-family: Arial, sans-serif;
    margin: 20px;
}

#filter {
    margin-bottom: 20px;
    padding: 8px;
    width: 300px;
}

.topic {
    margin-bottom: 10px;
}

.topic-header {
    cursor: pointer;
    background: #f0f0f0;
    padding: 10px;
    border: 1px solid #ccc;
}

.notes {
    display: none;
    padding-left: 20px;
}

.notes li {
    margin: 5px 0;
}