I'll take a look - although like Covarr, I won't have much opportunity to do a lot until after Christmas (albeit I'm short on time rather than funds...)
UPDATE: Made some progress; the OBB file, despite the name, isn't actually an obb file. (Probably due to Google's distribution rules; subsidiary data and patches are always named .obb regardless of file type). It's a fairly simple archive file format containing ~4900 data files. The data inside is far too repetitive to be compressed or encrypted (which surprises me, nowadays, if this is the exact same data that was distributed in the Android release - which seems likely - they didn't even apply LZ4 or something similar? Guess they don't care about wasting space on customer's phones.)
The archive doesn't appear to contain filenames: they may be encoded into the exe; or possibly that's the (only!) part of the archive that's obfuscated in some way.
Many of the data files have
suspiciously regular file sizes; just over 512KB, you say? Sounds an awful lot like a 256x512x32bit graphic, to me (also not compressed at all - not even PNG?!).
In fact, feeding those files into a raw image viewer gives us data like:

Looks an awful lot like some world map data, doesn't it? Albeit the colours are screwed, so it's not stored in straight RGBA.
Disappointingly it looks like a lot of the game data (all the dialogue?) is encoded into the EXE file, not stored in the OBB archive. That's a little annoying.
More to follow, presumably
