"... is to be friendly to the environment, not pollute"

Evironmentally friendly design is one that does not affect it's surroundings in a negative way.

An Environmental design:

• must obey the design philosophy surrounding it.
• should always try to extend existing designs positively and not pollute it.
• does not pollute existing code, introduce bugs or impact negatively
• tries to not repeat itself or existing artifacts
• does not pollute the minimal and maintainable design principles