static/style.css

body {
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    height: 100vh;
}

#whiteboard {
    flex-grow: 1;
}

#toolbar {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 10px;
    background-color: #A6B2FF;
}

#toolbar > * {
    margin: 0 10px;
}