body {
    font-family: Arial, sans-serif;
    background-color: #f4f4f4;
    margin: 0;
    padding: 20px;
}

#container {
    max-width: 800px;
    margin: auto;
}

.tree {
    margin-left: 20px;
}

.box {
    border: 1px solid #333;
    padding: 10px;
    margin: 5px;
    background-color: #fff;
    position: relative;
}

.add-button {
    margin-top: 10px;
    cursor: pointer;
    background-color: #28a745;
    color: white;
    border: none;
    padding: 5px 10px;
    border-radius: 5px;
}

.add-button:hover {
    background-color: #218838;
}