You may use the map-* tiles under the ISC license or CC-BY 4
http://creativecommons.org/licenses/by/4.0/, as you wish. They've all been
drawn using the ../scripts/drawtile script.

The letter-* tiles are generated with ../scripts/make-fonts.pl using the Source
Code Pro open font (you need to install it separately and adjust the path if
necessary).

All tiles are then embedded in ../images.go using the
../scripts/gen-images.goal script.
