World of Goo creator's rules for levels

While reading an interview with 2D Boy (World of Goo), Kyle Gabler said this

"1. No level can rely on luck or randomness. Luck causes frustration!
2. No level can be like any other level. Always introduce something new.
3. Every level must be visually distinct and iconic. Helps build them fiction of the world."

I shall consider these rules when creating my levels for Plectrum.

Full interview http://www.blogger.com/post-create.g?blogID=5839291477479315906