I handled the branding, user interface and most of the UX (as we worked on that together). Avoiding a rigid process and rather developing things as we went, it was a lot of fun, with plenty more features, enhancements and themes to come.
We designed and built our own customisable "themes" using the open-souce visual editor Maputnik for the Mapbox Style Specification. Learning about the deep world of map building which included OpenMapTiles (hill shading, contour lines, public spaces, etc.) and visual rankings of map elements at different zoom levels was both fun and tedious at times!