When using the Aspire UI library, there is no particular base class you need to extend for your application. Just the native flash.display.Sprite class would do.
The following is a template you may want to use:
ActionScript 3.0 MyApplication class
1: package 2: { 3: import com.ghostwire.ui.managers.uiSkin; 4: 5: import flash.display.Sprite; 6: import flash.events.Event; 7: 8: public class MyApplication extends Sprite 9: { 10: public function MyApplication() 11: { 12: if (stage) init(); 13: else addEventListener(Event.ADDED_TO_STAGE, init); 14: } 15: 16: private function init(evt:Event = null):void 17: { 18: removeEventListener(Event.ADDED_TO_STAGE, init); 19: 20: // ** uncomment to use "classic" theme ** 21: // uiSkins.initialize("classic"); 22: 23: // ** optional but recommended ** 24: // ** let assets preload before starting application ** 25: uiSkins.manager.addEventListener(Event.INIT, main); 26: } 27: 28: private function main(evt:Event):void 29: { 30: // ** main application code ** 31: } 32: } 33: }