Thank you, this is a lovely example. You mentioned that "I tried doing data = NULL or fill = "grey"" but it didn't work. Instead you can replace geom_map with geom_polygon to overcome this.

e.g.
geom_polygon(data = world_map,
aes(long, lat, group = group),
show.legend = FALSE, fill = "#DEDEDE66",
colour = "#818181", size = .15)

That's very cool, thanks very much for this!

Thanks a lot, this really saved me haha