Services
A service is a single instance of an object that gets updated, drawn, and loaded as needed. Services arent asynchronously loaded. You can only have one instance of each possible service class in the Services stack at any given time.
Adding a service
Engine.AddService(...)
Using a service
Engine.ServiceOf<Type>()
Which returns the first instance of a service of the type "Type", it will return default(T) if it does not find that service in the stack.