A good game teaches you how to play it

What you eventually discover as you continue to play is that Portal is a game about escaping from rooms that operate according to rules you are unaware of. You learn that each room is a puzzle, increasingly booby-trapped, and the game requires you to understand more and more complex physics in order to get out. If you don’t teach yourself the physics of each new room— that is, if you don’t learn the rules of the game—you’ll be stuck there forever, listening to the AI system repeat h...

 A good game keeps you at the edge of your ability

As you successfully lock in Tetris puzzle pieces, you get three kinds of feedback: visual—you can see row after row of pieces disappearing with a satisfying poof; quantitative—a prominently displayed score constantly ticks upward; and qualitative—you experience a steady increase in how challenging the game feels. This variety and intensity of feedback is the most important difference between digital and nondigital games. In computer and video games, the interactive loop is satisfyingly...