I was the sole front-end developer for MyFinance as part of a distributed development team. I worked with 3 other developers who were all back-end, so the front-end of the stack was my responsibility to build and maintain.
When I joined the company on a remote contract, there was a small amount of existing Angular code that was developed by one of the founders but was in need of cleaning up and organizing. I fully implemented the John Papa style guide across the entire project and grew the angular portion of the codebase by 80% over 5 months.
About two months into the contract, an entire redesign of the site was ordered, and I was required to port the site to the new design. The existing CSS was a Bootstrap theme and I made the decision to construct our own theme based on object oriented BEM principles. This created a much cleaner CSS codebase that will scale significantly better than Bootstrap if only because it will be considerably easier to maintain and add onto.