They say chess takes a day to learn and a lifetime to master. On the other hand, children have mastered the idea of playing make believe, but it takes a lifetime to learn the rules of TRPGs.
QUAD strives for two goals: to be fairly simple and simply fair. The game is designed to be short and simple to learn, with enough possibilities to keep veteran players interested.
The character creation system is designed so you can create a detailed character quickly. It also strives to create balanced characters: there should be no ways to 'max out' the rules to make a character more powerful than she should be.
One inherent downsiide of simplicity is that realism suffers. QUAD doesn't claim to recreate real life; it is a game designed to allow action and adventure. QUAD does make some attempts to maintain realism as a means of game balance.