By default, the white squares in the plot denote the lights that are on, and
black ones for the off. When you click on a light, this light as well as the
four neighbors will switch theirs status. Your mission is to close all the
lights.
# NOT RUN {## should use Xlib for the x11() device under *nix, e.gif (interactive()) {
if (.Platform$OS.type == "windows")
x11() else x11(type = "Xlib")
lights_out()
}
# }