Clark Aldrich summarizes some of the major elements he looks for in serious games, including an interactive world, level components, small and larger challenges, and rigorous assessment. The rigorous assessment "may use a traditional presentation of material that lines up with the destination application, such as in a test or real world problem. This can serve to "prove" that the player has really learned something of value." All good, but I think there are elements missing; when I think of the disappointment that is Civilization V (which contains all Aldrich's items) these items spring to mind: speed of execution (Civ V runs slooowly), rational response (opponent Civs 'denounce' you even when you've done nothing), easing of repetition (Civ V makes you do the same pointless things (like bombing a city) over and over), and the like. These all roll up under the category of 'playability', an aspect without which your game (like Civilization V) is dead in the water.