Consider your own product. Is it fun, even without a goal? Does it indulge moments of playful exploration? Does it create moments of pleasant surprise? If so, congratulations because then you have a toy and you're on the way to building a great game.

As it turns out, there is no unifying theory of game design. To create games, we have to draw upon the art and science of psychology, mathematics, interaction design, and storytelling.

Superhuman is productivity software, but I'm really a gamer at heart — and I've built a framework for applying game design to business software.