A great game seduces its player into flow state. Since we know a lot about what flow state is and what it requires, you might imagine that game's design to be a lot of work, but not mysterious. Yet 99% of all games fail. The vast majority of game designers have never designed an addictive game. In HCI research, games are analyzed based on flow state properties but that's descriptive, not prescriptive. Designing such games remains mystical. Like other performing arts, game design needs accident, luck, inspiration, perspiration, and knowledge. I would like to justify my being invited to talk so on top of the skeleton of flow, I will add some meat that you would not likely hear from anyone else. I will talk about what I learned playtesting my own work and what I was taught by great game designers, in creating games that were indeed addictive. As such, this will be a very idiosyncratic and personal introduction to the art of designing irresistible engagement.