align.bottom(offset)

Position the layer to the bottom of its parent. If there is no parent, it will use the Screen. Bottom only works for the y layer property. It can be used as a property, in states and in animations.
译： 把图层置于它的父级的底部。如果没有父级，就放在设备屏幕底部。Bottom只对图层的y属性起作用，它可以作用在属性、状态及动画中。

Arguments(参数)

offset — 一个数字（可选）

layerA = new Layer
    y: Align.bottom

layerB = new Layer
    y: Align.bottom(-100) # 100 pixels from the bottom