The depth of this Game Object within the Scene.
The depth is also known as the 'z-index' in some environments, and allows you to change the rendering order of Game Objects, without actually moving their position in the display list.
The default depth is zero. A Game Object with a higher depth value will always render in front of one with a lower value.
Setting the depth will queue a depth sort event within the Scene.
The depth of this Game Object.
This Game Object instance.