Difficulty Curves in an AS3 Defence Game

How hard is a wave of enemies? If the enemies get twice as strong as the player gets twice as strong there is no change in difficulty. The difficulty of a defence game is related to the ratio of power between the enemies and the player. Over time the player buys upgrades and gets stronger, and the strength of the enemies must match that closely to make the game challenging, fun and progressively more difficult.

Adding horses to a game world is not an easy thing to do. The sculpting, animating, and AI behaviours required to model a four legged creature are all more than twice as complex as for a biped. But the steppe simply would not be the same without mounted scouts and fiendish bandits so horses had [...]