The demo is useable as is (complete with working authentication examples) or you can download, branch, and build on it. This solution uses Polymer and Brightspace UI components to create a UI with the same styles Brightspace Daylight uses. The readme has a lot of different links to resources and can be used as a great starting point for getting an LTI application up and running in your Brightspace environment.
Link: https://github.com/Brightspace/Awards-Leaderboard