void GameWorld::CreateGame()
{
  // initialise counters & flags
  seconds_ = 0;
  enemies_killed_total_ = 0;
  enemies_killed_combo_ = 0;
  combo_timer_ = 0;
  score_ = 0;
  is_popup_active_ = false;

  // add the stars
  background_ = BackgroundManager::create();
  addChild(background_, E_LAYER_BACKGROUND);

  CreateBoundary();
  CreatePlayer();
  CreateContainers();
  CreateHUD();

  // initially add some enemies & a powerup
  AddEnemyFormation();
  AddPowerUp();

  // schedule the update and the tick
  scheduleUpdate();
  schedule(schedule_selector(GameWorld::Tick), 1.0f);
}