I spent last weekend at CODEX Hackathon working on a tool called LitRen. LitRen is meant to make ebooks editable and annotatable. The idea behind this project was that editable ebooks would help people who write fan fiction: fanfic authors could insert their ideas and stories into ebooks, or even modify the existing text as they like. With public domain books, entirely reimagined versions of the story could be created by modifying and expanding on the original text.
Making this annotation tool required some heavy lifting in javascript. There are some existing javascript annotation tools that we adapted to work with ebooks. As much of the javascript was over my head, my small contribution was to watch others code, and to build a responsive landing page with Bootstrap.
By the end of the weekend, the basic annotation/editing tool was working, though a lot of supporting functionality remained unbuilt. That was fine; our goal was to have a proof of concept. Anyhow, it was a fun project and a great weekend!