Material icons are beautifully crafted, delightful, and easy to use in your web, Android, and iOS projects.
Design
Design and User Experience Guidelines for Fire TV
This document provides guidelines for the design and user experience of applications for the family of Amazon Fire TV devices.
Google Android Design Guides
Up and running with material design.
Apple Developer Design Guides
Get in-depth information on how to design successfully for Apple platforms with these standards and principles.