Since Athens is about drawing graphics, we need a media where all drawing operations will appear. We call that media a surface. The surface is abstract. It can have set dimensions, or don't. We don't define if it representing some kind of physical surface (like part of the display screen), or how it storing the data inside. We leaving an introduction of such details to concrete surface implementation. All that matters is that surface is a final target of all our drawing operations. Therefore, in Athens, a surface is usually a starting point where all begins from, and you doing so by creating a specific surface. It is surface's responsibility then, to provide user a means how he can draw on it, and therefore there is a number of factory methods, that allowing you to create a canvas, paints and shapes. All those three are specific implementation of AthensCanvas, AthensPaint and AthensShape protocols, suitable to be used with specific surface implementation that you using.
