"The lesson games have for design is not really a lesson about games at all. It’s a lesson about play. Play isn’t leisure or distraction or the opposite of work. Nor is it doing whatever you want. Play is the work of working something, of figuring out what it does and determining how to operate it. Like a woodworker works wood. By accepting the constraints of an object like a guitar (or like Tetris), the player can proceed to determine what new acts are possible with that object. The pleasure of play—the thing we call fun—is actually just the discovery of that novel action." Not just this quotation, but all of this article, really. So good. Immaterials, again.