Twilight isn't very opinionated when it comes to Javascript or CSS, however you can write these directly inside your components using the special Style and Script components. These will be extracted and saved as a css and js files.

<a :href="href" class="btn">
    <Children />
</a>

<Style>
    .btn {
        background: blue;
        color: white;
    }
</Style>

<Script>
    console.log('Hello from the button');
</Script>

These will be saved in the assets directory, which can be set on the Compiler.

assets/
    components/
        Button/
            style.css
            script.js