I want to draw the density line on the scatter plot using ggplot2.
Referencing this code, I draw the example figure below:

set.seed(1)
df <- data.frame(x = rnorm(200), y = rnorm(200))

ggplot(df, aes(x = x, y = y)) +
  geom_point() + 
  geom_density_2d()

The expected result is here.