This document provides a brief introduction to game design concepts. It defines a game as a system where players engage in an artificial conflict with rules and a quantifiable outcome. Games exist within the "magic circle" and have formal elements like players, objectives, and resources. They also incorporate dramatic elements such as challenge, play types, character, and story. Challenge must match a player's abilities to create a state of "flow." Play can take competitive, chance-based, make-believe, or vertigo forms. Character and story engage players and drive games forward through objectives, choices, and emerging narratives.