Creating tilings from a group of polylines.. my first project

Hi,

I am new to grasshopper but have some Rhino and programming experience. My first grasshopper project is to create a 2d tiling by mirroring and coping a
group of polylines into a rectilinear grid. Kids play I know but got to
start some where. I would like to do it in a generic way so I can feed
it different groups of polylines and thereby generate different tilings. This
is the first step in a larger project.

My first thought was to first determine the overall size of the polyline group. I would use those dimensions to generate the grid. Thus far I haven't been able to find a way to get the bounding box for the polyline group.

Is there a straightforward way to do this.... get the overall dimensions of a
group of non-joinable polylines. Grouping them in Rhino doesn't work..
Grasshopper prefers to give bounding box to each polyline separately.

I suppose one could get the beginning and end points of all the lines and then
find the min and max, but that seems to be the long way around. Or perhaps it
would be better to copy and mirror each line separately. I would be
thankful for some help/opinions.

I have included a picture of (1) polyline group and (2) the resulting tiling which
results from copying and mirroring it.