how to draw a radar chart with a lot of rows (or dimensions) using R?

Let's say I have such data:

a <- tibble(id=c(1,1.1,1.2,1.7,2,2.1,2.6,4,4.6,4.68),
            x=c(0.3,0.5,0.2,0.7,0.1,0.5,0.43,0.6,0.3,0.65),
            y=c(0.2,0.1,0.22,0.1,0.5,0.2,0.3,0.2,0.14,0.3))

This is just a sample, my real data is much more than this. and x+y+... = 1. I want to draw two lines: one line is for x, one line is for x+y:

ggplot(a) +
  geom_line(aes(x=id,y=x),color='red') +
  geom_line(aes(x=id,y=x+y),color='blue')

But what I really want it sth like a radar chart like:

You can see there is a circle with the radius to be 1. x and x+y, (maybe more in my data) are red and blue circles respectively. So, x+y must be larger than x but always in the circle because x+y+...=1. My data has a lot of ids, so it is not the traditional radar with few dimensions.

So, could anyone please help me out here?