A bit over a year ago I made a set of one-off maps with some improvements, and I've now ported those improvements over to the main map:

The changes are:

• Instead of a rainbow color map, it's now using the "magma" perceptually neutral map. This is a series of colors which people perceive as evenly spaced, and which also look reasonable if you're color blind.

• Instead of the bucket definitions changing each month as the system tries to maintain equal area, I've set fixed buckets. This makes paging through the maps over time to see changes much more informative: a given shade on the 2019-06-18 map means the same thing as on the 2011-06-16 map.

• It works with python3.

You can play around with it here, and the code is on github.