textual/docs/examples/styles/box_sizing.tcss

#static1 {
    box-sizing: border-box;
}

#static2 {
    box-sizing: content-box;
}

Screen {
    background: white;
    color: black;
}

App Static {
    background: blue 20%;
    height: 5;
    margin: 2;
    padding: 1;
    border: wide black;
}