Starling handbook Preview

Figure 4. Starling’s coordinate system has its root at the top left.
We also accessed the stage object and queried its height. The Stage describes the area to which
everything is rendered; it is the very root of the display list (and parent of the Game instance we are
working with right now).
Organizing the Code
It’s nice that there is something on the screen now — but before going on, we need to ponder a little
bit about how we’re going to organize all of the code we’re going to write.
Of course, we could put all of our game elements right into the Game class, but that’s going to get
messy quickly. Instead, it’s a good idea to split the game up into logical units; each with a very
limited responsibility.
After all, we’re not only going to create this landscape with the flying bird, but also a title screen,
maybe a leaderboard, etc. But how should we organize all these elements?
Introducing: The Sprite!
You have already seen this class before: our Game class is extending Sprite. This class is one of the
most important building blocks within Starling. It’s a container that can group together multiple
elements.
Here’s a simple example showing a typical use-case of a sprite:
var body:Image = ...;
var tail:Image = ...;
var beak:Image = ...;
var bird:Sprite = new Sprite();
bird.addChild(body);
bird.addChild(tail);
bird.addChild(beak);
addChild(bird);
The bird object now contains body, tail and beak, grouped together in one object. When you want to
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