The success of an interactive storytelling experience depends on a balanced dramatic structure and user agency. A dramatically interesting narrative experience is one that moderates tension between characters and events over time, such that conflicts arise logically and are not left without resolution. It must also differ noticeably on every "playthrough" as a function of the user's freedom to interact with characters and objects in the virtual world. This can be achieved to varying degrees of success by branching, emergent, character-driven, and plot-driven systems, but no existing system fully achieves a lifelike experience. AIs do not yet have a human grasp of the rules of drama and narrative, so existing interactive dramas produce a limited number of significantly different story outcomes, relative to the amount of labor required of the author.