About a month ago, there was a post on HN for free foreign exchange rates API (https://news.ycombinator.com/item?id=22979288)

The API was quite easy to understand and inspired me to do a one-day build challenge of making a web UI for the rates as I learn Javascript and D3.js.

Things I want to do but couldn't fit into deadline: better mobile reponsive, making it a "PWA".

Feedback is much appreciated.