How to create a shaded 2d density plot in ggplot2 and R

I would like to create a 2d density plot where depth of color represents density.

So for the data set

x1 <- rnorm(100, mean=0)
y1 <- rnorm(100, mean=0)
x2 <- rnorm(100, mean=4)
y2 <- rnorm(100, mean=4)

df <- data.frame(x = c(x1, x2), y=c(y1, y2), cat=rep(c("A", "B"), each=100))

I could make a contour plot

ggplot(df, aes(x=x, y=y, color=cat)) + geom_density2d()

...but instead of contours, I'd like for the image to have a strong orange color at the peak of the cat="A" data, fading out to transparency as the density decreases, and a strong cyan color at the peak of the cat="B" data, fading out as the density decreases.

It seems like some combination of geom_tile() and aes(alpha=cat) would do this, but I can't quite figure it out.

Do this:

# Create density plot with custom colors for categories A and B
ggplot(df, aes(x = x, y = y)) +
  stat_density_2d(
    aes(fill = cat, alpha = after_stat(level)), 
    geom = "polygon",
    color = NA
  ) +
  scale_fill_manual(
    values = c("A" = "darkorange", "B" = "cyan2"),
    name = "Category",  # Legend title
    guide = "legend"
  ) +
  scale_alpha(range = c(0, 0.5), guide = "none") 

refer this for colors.

For completenes, me personally I would do something like this:

# Create density plot with custom colors and density outlines
ggplot(df, aes(x = x, y = y)) +
  stat_density_2d(
    aes(fill = cat, alpha = after_stat(level)), 
    geom = "polygon",
    color = NA
  ) +
  geom_density_2d(
    aes(color = cat), 
    size = 0.5,  # Line thickness for the contours
    linetype = "solid"
  ) +
  scale_fill_manual(
    values = c("A" = "darkorange", "B" = "cyan2"),
    name = "Category",  # Legend title
    guide = "none"
  ) +
  scale_alpha(range = c(0.0, 1), guide = "none") +
  scale_color_manual(
    values = c("A" = "darkorange", "B" = "cyan2")
  ) +
  theme_minimal() +
  labs(title = "2D Density Plot by Category with Density Outlines",
       x = "X",
       y = "Y")

gives you a clearer picture!