Pretty neat. One tip it took me a while to realize is that after you tap on a country, the compass rose (now the same color as the country) can be used to rotate it.
But why do countries rotate to the left as you drag them north and rotate to the right as you drag them south?
I think part of that is an illusion, since for something bowing upwards, the usualy anchor point of top left seems rotated clockwise.
But there is still a real rotation - look at wyoming or colorado for a perfect rectangle. My guess is the div element isn't quite centered - perhaps too much padding on the right edge, causing the center point to be off to the right. So when it bows you get the rotation bias