As a semi-retired developer now playing with the new tools of the trade, I put this together (aka iterated with Claude over 12 weeks and about 300 km of runs), and this is what came out.
The biggest challenges were getting the zoom levels and transitions right as you race against up to 6 past versions of you and different performances, as well as the map detail in a way that would work for both road and trail runs.
I'm proud of it and would love for some of you to test it as well and have fun with it.