#foo {
    [type='foo'] {
        line-width: 1;
    }
    a/polygon-fill: black;
    b/building-height: 0.5;
    a/line-width: 10;
    b/line-width: 5;
    b/line-color: blue;
    a/line-color: red;

    [type='bar'] {
        line-width: 2;
    }
}