BackgroundLayer is a normal layer, but you don’t have to set its size or position; it will always assume the size of the screen.
By default it’s white, but you can give it another color.
bg = new BackgroundLayer backgroundColor: "#ccc"
Regarding Stacking order: This type of layer will always have an index of
-1 or lower.
One of the problems with background layers is that the
layer.sendToBack() function can place a layer underneath the background layer.
It’s now recommended to set the color of the
Screen.backgroundColor = "#fff"