Principles of Material Design: Material is the metaphor. A material metaphor is the unifying theory of a rationalized space and a system of motion.
Bold, graphic, intentional: The foundational elements of print-based design – typography, grids, space, scale, color, and use of imagery – guide visual treatments.
Motion provides meaning: Motion respects and reinforces the user as the prime mover. Primary user actions are inflection points that initiate motion, transforming the whole design