The document discusses the key elements of game design: core mechanics, secondary mechanics, progression elements, and narrative. It defines core mechanics as the fundamental interaction that drives the game, such as running/jumping in platformers or shooting in FPS games. Secondary mechanics add variety to the core mechanic, while progression elements like levels and power-ups encourage continued play. Finally, narrative provides the context for why the player progresses through the game. The document stresses that the most effective games have these elements working together in a complementary way.