Click the Settings button Open up the Template settings panel.

Alternately, you can click on the outer area around the canvas to open up the template settings.

On the right side, under the Global CSS section (5.), create your custom CSS rules.

Your custom rules can be reused throughout your layers using the corresponding Class name.

Example of Global CSS:

.piece{
    text-shadow: 1px 1px black;
}
.piece-black{
    text-shadow: 1px 1px white;
}

From there, on any layer, you can add the custom class “piece” or “piece-black” to apply the styles declared in the Global CSS section.