Parallel development

This weekend I finished my first game of XCOM. And I couldn't help but notice that way before the end I had reached a tipping point: Suddenly I had enough money for everything, and some of the battles became rather easy due to the experience and gear of my soldiers. Basically XCOM is a game of parallel development: You get stronger, and the aliens get stronger in parallel. The side who gets stronger the fastest ultimately wins. But as the challenge of the game depends on the difference in stats

World of Warkraft...