I used Web Mercator to flatten the map, so its "1:1" scale, but obviously not perfect because it is on a flat plane.

Neat project! It's an understandable limitation you had to commit to, but I'm curious how you've found the distortion away from the equator with Mercator. Probably not really noticeable in any major way within the arctic/antarctic circles but obviously closer to poles it's going to get quite wonky.