The goal of rsphere is to plot a 2D shaded sphere with a two-colours gradient.
You can install the development version from GitHub with:
# install.packages("remotes")
remotes::install_github("ahasverus/rsphere")
plot(x = 0, y = 0, asp = 1, xlim = c(-1, 1), ylim = c(-1, 1), axes = FALSE, ann = FALSE)
rsphere::add_sphere()
plot(x = 0, y = 0, asp = 1, xlim = c(-1, 1), ylim = c(-1, 1), axes = FALSE, ann = FALSE)
rsphere::add_sphere(x1 = 0.5, y1 = -0.5, col = c("black", "red"))