Backing to Xemuth I think you made grate work here and probably you had a lot of fun writing this application. I am glad you decided to publish it as an open source. We definitely need more initiative like this. Thanks and good luck in developing this project and other projects in the future!

At the end, I would like to give you some power tips for the future. I notice that you use following code in your header files (.h):

using namespace Upp;

This should be avoided at all cost, because when somebody includes that file it will also inherit this namespace shortcut. To overcome that issue you can put your class into Upp namespace or directly use namespace Upp::. You can find more information on https://stackoverflow.com/questions/5849457/using-namespace- in-c-headers.

Sometimes you pass string as a copy when you can pass it by const reference to avoid copy:

GameObject::GameObject(String _name){ // <- Copy
	name = _name; // <- Copy one more time
}

Should be replace with

GameObject::GameObject(const String& _name){ // <- No copy, address (reference) is passed
	name = _name; // <- Copy
}

As you may see with const& we avoid one extra copy that is not need in above case.