Referring to the visual's iframe element from CSS

Hi,

Is it possible to do this? For example to set the background of my visual, I've tried the following:

#sandbox-host{
    background:black;
}

but it has no effect.

Strangely enough, in the visual's TypeScript I can set it with d3 like 

d3.select(this.host).style("background", "black");

so it is possible to style it, just not via pure CSS it seems.

Am I doing something wrong?