<style>
:root {
    --foo: green;
}
</style>
<div id="myShadowHost">
<template shadowrootmode="open">
<style>
span { color: var(--foo, red); }
</style>
<span>green</span>
</template>
</div>
<script src="../include.js"></script>
<script>
    test(() => {
        let span = myShadowHost.shadowRoot.firstElementChild.nextElementSibling;
        println(getComputedStyle(span).color);
    });
</script>