I'm also having a issue with custom css properties.
For example, this isn't working:
I believe this is a problem with Errai because it works properly in the browser's developer console,
but doesn't show up if it is put into a style sheet for a Templated class.
for example: @Templated(provider = HomeTemplateProvider.class, stylesheet = "home.css")
Any media selectors, calc functions, or custom properties in home.css won't work.
They will however work if they are put into the index page, but this is not ideal.