Try setting the class as follows:
.domain {
fill: none;
stroke: black;
stroke-width; 1;
}
The domain is actually a path (perhaps the css selector can be
path.domain) that regularly looks something like this:
|____________________________|
It has ticks (as defined by the tickSize) on both sides. If the fill
is set to something then it becomes a rectangle of height tickSize.
In your case setting the fill to none avoids this behavior. Setting
the stroke should give you the desired outcome.
- Ricardo