Managing Game Rules

1. Create a new C# component and call it LevelManager.
2. Open the LevelManager component in an IDE and copy the code below. Save your code in an IDE to ensure it's automatic compilation on switching back to UnigineEditor.
   Source code (C#)

   public class LevelManager : Component
   {
   	// level timer
   	public float timer = 100.0f; 
   
   	public event Action endGameEvent;
   
   	bool isCounting = true;
   
   	int physicalObjectsNum;
   	
   	WidgetLabel widget_timer, widget_goal;
   
   	ObjectText endText;
   
   	void Init()
   	{
   		InitGUI();
   		
   		// find the object text node of the widget
   		endText = Game.Player.FindNode("header_text", 1) as ObjectText;
   
   		// count dynamic objects in the level
   		physicalObjectsNum = node.NumChildren;
   	}
   
   	void InitGUI()
   	{
   		// getting a GUI pointer
   		Gui gui = Gui.Get();
   
   		// creating a label widget and setting up its parameters
   		widget_timer = new WidgetLabel(gui, "Time Left:");
   		widget_timer.SetPosition(10, 10);
   		widget_timer.FontColor = vec4.RED;
   
   		widget_goal = new WidgetLabel(gui, "Objects Left: ");
   		widget_goal.SetPosition(10, 30);
   		widget_goal.FontColor = vec4.BLUE; 
   
   		// add widgets to the GUI
   		gui.AddChild(widget_timer, Gui.ALIGN_OVERLAP);
   		gui.AddChild(widget_goal, Gui.ALIGN_OVERLAP);
   	}
   	
   	void Update()
   	{
   		// decrease the timer
   		if (isCounting)
   		{
   			timer -= Game.IFps;
   			if (timer <= 0)
   			{
   				//set end game text
   				endText.Text = "Game Over";
   				endGameEvent?.Invoke();
   				isCounting = false;
   			}
   		}
   
   		//win
   		if (physicalObjectsNum <= 0)
   		{
   			endText.Text = "Success!";
   			endGameEvent?.Invoke();
   			isCounting = false;
   		}
   
   		// show the current time and objects left to clear
   		if (isCounting)
   		{
   			widget_timer.Text = "Time Left: " + timer.ToString("0.0") + " s";
   			widget_goal.Text = "Objects Left: " + physicalObjectsNum.ToString();
   		}
   		//hide the widgets on end game
   		else
   		{
   			widget_timer.Enabled = false;
   			widget_goal.Enabled = false;
   		}
   	}
   
   	void Shutdown()
   	{
   		widget_timer.DeleteLater();
   		widget_goal.DeleteLater();
   	}
   
   	public void DecPhysicalObjectsNum()
   	{
   		physicalObjectsNum--;
   	}
   }

3. Create a new Dummy Node called "level_manager" and place it somewhere in the world.
4. Add the LevelManager component to the level_manager node.
   

We created the system GUI via the API from the code. The alternative method is to use UI files.

1. Open the KillZone component in your IDE, add a levelManager field and replace the content of Enter callback function according to the following code. Save your code in an IDE to ensure it's automatic compilation on switching back to UnigineEditor.
   KillZone.cs

   public class KillZone : Component
   {
   	// the area into which an object should fall
   	WorldTrigger trigger;
   
   //========================== NEW - BEGIN ===============================
   	LevelManager levelManager;
   //=========================== NEW - END ================================	
   
   	void Init()
   	{
   		trigger = node as WorldTrigger;
   
   		if (trigger != null)
   			trigger.AddEnterCallback(Enter); // set the handler to be executed when an object enters the area
   	}
   
   //========================== NEW - BEGIN ===============================	
   	void Enter(Node target)
   	{
   		levelManager = target.GetComponentInParent<LevelManager>();
   		// check if the parent node has a LevelManager component attached
   		if (levelManager != null)
   		{
   			// delete the entered node and decrease the amount of physical objects
   			levelManager.DecPhysicalObjectsNum();
   			target.DeleteLater();
   		}
   	}
   //=========================== NEW - END ================================		
   }

2. Let's set the level_manager node as a parent to physical objects. Open the ObjectGenerator component in your IDE and replace the code with the following. Save the code in your IDE and switch back to UnigineEditor.
   ObjectGenerator.cs (C#)

   public class ObjectGenerator : Component
   {
   //========================== NEW - BEGIN ===============================
   	public Node levelManager;
   //=========================== NEW - END ================================
   
   	private void Init()
   	{
   //========================== NEW - BEGIN ===============================
   		if (levelManager)
   		{
   //=========================== NEW - END ================================
   			// cube 
   			Mesh meshBox = new Mesh();
   			meshBox.AddBoxSurface("box_surface", new vec3(1.0f));
   			ObjectMeshStatic box = new ObjectMeshStatic(meshBox);
   			//========================== NEW - BEGIN ===============================
   			box.Parent = levelManager;
   			//========================== NEW - END ===============================
   			box.TriggerInteractionEnabled = true;
   			box.SetIntersectionMask(0x00000080, meshBox.FindSurface("box_surface")); // check the BulletIntersection bit
   			box.WorldTransform = MathLib.Translate(new vec3(0.5f, 7.5f, 1.0f));
   			box.SetMaterial("mesh_base_0", "*");
   			box.Name = "box";
   			BodyRigid bodyBox = new BodyRigid(box);
   			ShapeBox shapeBox = new ShapeBox(bodyBox, new vec3(1.0f));
   			new ShapeSphere(bodyBox, 0.5f);
   			bodyBox.ShapeBased = false;
   			bodyBox.Mass = 2.0f;
   
   			// sphere
   			Mesh meshShpere = new Mesh();
   			meshShpere.AddSphereSurface("sphere_surface", 0.5f, 9, 32);
   			ObjectMeshStatic sphere = new ObjectMeshStatic(meshShpere);
   			//========================== NEW - BEGIN ===============================
   			sphere.Parent = levelManager;
   			//========================== NEW - END ===============================
   			sphere.TriggerInteractionEnabled = true;
   			sphere.SetIntersectionMask(0x00000080, meshShpere.FindSurface("sphere_surface")); // check the BulletIntersection bit
   			sphere.WorldTransform = MathLib.Translate(new vec3(4.5f, 5.5f, 1.0f));
   			sphere.SetMaterial("mesh_base_1", "*");
   			sphere.Name = "sphere";
   			BodyRigid bodySphere = new BodyRigid(sphere);
   			new ShapeSphere(bodySphere, 0.5f);
   			bodySphere.ShapeBased = false;
   			bodySphere.Mass = 2.0f;
   
   			// capsule
   			Mesh meshCapsule = new Mesh();
   			meshCapsule.AddCapsuleSurface("capsule_surface", 0.5f, 1.0f, 9, 32);
   			ObjectMeshStatic capsule = new ObjectMeshStatic(meshCapsule);
   			//========================== NEW - BEGIN ===============================
   			capsule.Parent = levelManager;
   			//========================== NEW - END ===============================
   			capsule.TriggerInteractionEnabled = true;
   			capsule.SetIntersectionMask(0x00000080, meshCapsule.FindSurface("capsule_surface")); // check the BulletIntersection bit
   			capsule.WorldTransform = MathLib.Translate(new vec3(4.5f, 0.5f, 3.0f));
   			capsule.SetMaterial("mesh_base_2", "*");
   			capsule.Name = "capsule";
   			BodyRigid bodyCapsule = new BodyRigid(capsule);
   			new ShapeCapsule(bodyCapsule, 0.5f, 1.0f);
   			bodyCapsule.ShapeBased = false;
   			bodyCapsule.Mass = 2.0f;
   //========================== NEW - BEGIN ===============================
   		}	
   //=========================== NEW - END ================================
   	}
   }

3. Select the object_generator node in the World Nodes window and drag the level_manager node to the corresponding field of the ObjectGenerator component.
   
4. Save changes to the world, go to File->Save World or press Ctrl+S hotkey. Then run the game to see the game rules in action.