This extension creates a second stage which sits on top of the root starling stage, allowing the root stage to stretch to fit the size of the screen without distorting your assets. The second stage maintains your desired aspect ratio, scaling up using the “show all” or “letterbox” method. The extension provides several properties to easily position your objects relative to screen edges, or to the stage.
Instead of initializing Starling the traditional way, replace the call to new Starling() with the following code:
var mStarling:Starling = FullScreenExtension.createStarling(Game, stage, width, height);
Then, whenever you add something to either your root class or to Starling.current.stage, add it instead to FullScreenExtension.stage. Example:
Full explanation and tutorial: http://www.Brinkbit.com/blog/starling-fullscreen-extension/
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