body {
    margin: 0;
    background: #f4f4f4;
    font-family: sans-serif;
}

#toolbar {
    display: flex;
    justify-content: center;
    align-items: center;
    background: #333;
    color: white;
    height: 50px;
}

#toolbar button {
    margin: 0 8px;
    padding: 6px 12px;
    border: none;
    background: #666;
    color: white;
    border-radius: 4px;
    font-size: 14px;
}

#toolbar button:hover {
    background: #888;
}

#viewer {
    width: 100%;
    height: calc(100vh - 50px);
    overflow: hidden;
}