[intro video](https://www.youtube.com/watch?v=HQ_ytw58tC4)
[list view](https://www.youtube.com/watch?v=k1LxTsmAURU)
[fl chart](https://www.youtube.com/watch?v=hVRU-kpKNjQ&list=PL1-_rCwRcnbNpvodmbt43O81wMUdBv8-a)