Couple questions on TDN Strategy Tutorial

// --------------------------------------------------------------------
// t2dSceneObject::onSelected()
//
// This is the function all objects pass through when selected
// it places the description text that comes directly from the object
// and places it into a temporary GUI that gets attached to the 
// description section of the Object Properties box
// --------------------------------------------------------------------
function t2dSceneObject::onSelected(%this, %pos)
{
   %this.type.onSelected(%this, %pos);
}

// --------------------------------------------------------------------
// SceneWindow2D::onMouseEnter()
//
// This function is triggered from the engine when the mouse enters the screen
// --------------------------------------------------------------------
function SceneWindow2D::onMouseEnter(%this, %modifier, %worldPos, %mouseClicks)
{
   // when we enter the screen we want to re move the mouseLeftGui warning
   mainScreenGui.remove(mouseLeftGui);
   // enable camera panning with a delay so we don't pan as we move in from 
   // outside the game window
   schedule(300, 0, "enablePan");
}

// --------------------------------------------------------------------
// SceneWindow2D::onMouseLeave()
//
// This function is triggered from the engine when the mouse leaves the screen
// --------------------------------------------------------------------
function SceneWindow2D::onMouseLeave(%this, %modifier, %worldPos, %mouseClicks)
{
   // generate the mouse left gui to warn us our mouse has left
   // this is mainly for debuging purposes
   new GuiMLTextCtrl(mouseLeftGui) { 
      text = "MOUSE LEFT"; 
      extent = "50 50";
      position = "350 10";
   };

   // add the control
   mainScreenGui.add(mouseLeftGui);

   // stop all panning of the camera so the camera isn't constantly moving
   // while we're out of the game wi
   stopAllPanning();
   
   // here we check each panning direction, if we're panning then we stop panning
   if($panningLeft)
   {
      stopPanning(Left);      
   }
   
   if($panningRight)
   {
      stopPanning(Right);      
   }
   
   if($panningUp)
   {
      stopPanning(Up);      
   }
   
   if($panningDown)
   {
      stopPanning(Down);      
   }
   
   // here we disable panning while we're out of the window
   disablePan();
}

// --------------------------------------------------------------------
// Setup T2D Scene.
// --------------------------------------------------------------------
function setupT2DScene()
{
	// Create t2dSceneGraph.
	new t2dSceneGraph(t2dScene);
	
	// Associate Scenegraph with Window.
	sceneWindow2D.setSceneGraph( t2dScene );
	
	// Set Camera Position to be centered on (0,0) with
	// view width/height of (100/65).
      $cameraPos = "0 0 100 65";
	sceneWindow2D.setCurrentCameraPosition( "0 0 100 65" );

	
	// ************************************************************************
	//
	// Add your custom code here...
	//
	// ************************************************************************
	
	onStartUp();
}

gameData.circles.base = gameData.spawnObject(CirclesBase, circles, "75 -77", "CircleBase");