Anni Chen

- [x] For each exercise with solutions, maybe add a link directly to the page of solutions in section 15; Also add the exercise numbers in section '15 Solutions' to...

> Same opinion as Jason on section 6, and instead of directly giving an HTML code to download, it's better to provide instructions that can be interactive on the page,...

- [x] For section 11.4 Blockbuilder 2015-2020, the link direct to [Mike Bostock](https://bl.ocks.org/mbostock) shows that the author no longer maintains the codes on Blockbuilder and instead moves all of the...