Source: https://www.youtube.com/watch?v=tffX3VljTtI (11 mins in)

Warren Spector's 6 + 2 + 1:

• What's the core idea?
• Why do this game? Commercial hit? No choice?
• What are the dev challenges? Hard is ok, impossible not good
• Is this idea well-suited to games? Games are about DOING, not BEING
• What's the fantasy? If no fantasy, bad idea
• What are the verbs? Games are about Doing
• Has anyone done this before? If no - could be a bad idea, or good, just be careful
• What's the ONE thing? ONE new thing that hasn't been done before
• Do you have something to say? An issue/theme to explore