Material Design: Google Design Guidelines

Reposting this because of what these guidelines did for me. If I were to recommend one set of guidelines for interaction design, this would be it.

A material metaphor is the unifying theory of a rationalized space and a system of motion. The material is grounded in tactile reality, inspired by the study of paper and ink, yet technologically advanced and open to imagination and magic.

Check it out in the link below...