l::before {
    content: "";
    width: 100px;
    height: 100px;
    background: orange;
    display: block;
}
p { writing-mode: horizontal-tb; margin: 0;}
body {
    margin: 0;
    width: 200px;
    height: 200px;
    writing-mode: vertical-rl;
}
html {
    contain: style;
}
</style>

<p>Test passes if the orange square is in the upper-left corner.
