BackgroundLayer

A background layer is just a normal layer, but it scales with your window, so it always covers the entire canvas. If the background layer has a parent, the background will inherit the size of the parent.
译：背景图层其实也是一种普通图层，只不过他会充满整个窗口，因此它会覆盖整个画布。如果一个背景图层还有父图层，那么他就会继承父级图层的尺寸。

layerA = new BackgroundLayer
    backgroundColor: "white"

Colors can be defined by keywords, but also rgb and hex values.
译：你可以通过backgroundColor给其定义一个背景色，支持rgb和hex色值。

# Hex value for white 
layerA = new BackgroundLayer
    backgroundColor: "#ffffff"

# RGB value for white 
layerA = new BackgroundLayer
    backgroundColor: "rgb(255,255,255)"

# RGBA value for white 
layerA = new BackgroundLayer
    backgroundColor: "rgba(255,255,255,1)"