Arch Linux

Ah, that is a funny one. teeworlds has the following logic to detect the data path :
1) use provided data-dir override
2) use data-dir in PWD if present
3) use compiled-in data-dir if present
4) check for usable path in argv[0]
5) check for all default locations

The problem is that I reached 2) because I was running the game from $HOME, and I have a $HOME/data directory, which has nothing to do with teeworlds.
For most people, it should use point 5), because the hardcoded default locations are : "/usr/share/teeworlds", "/usr/local/share/teeworlds"
and the one we use is /usr/share/teeworlds.

So I can still launch the game properly with either 1) teeworlds -d /usr/share/teeworlds
or 2) cd /usr/share/teeworlds ; teeworlds

To be on the safe side, I would suggest to provide a launch script which do either of these two solutions, so that the game works even when you run it from a directory which contains a "data" directory.

Code reference : http://teeworlds.com/trac/teeworlds/changeset/1522#file4

Wow... #2 is fairly stupid. I will add a launcher script on the next update (or perhaps earlier if I feel like closing bugs...)

This problem was found and fixed by gentoo : https://bugs.gentoo.org/attachment.cgi?id=180630&action=view
And the patches were submitted upstream : http://www.freelists.org/post/teeworlds/PATCHES-Fix-datadir-search
I got a confirmation from teeworlds' developer on IRC that they will be applied in next version.

The main fix is to only use valid datadir by checking for the existence of the mapres dir inside.
Since the patches remove the need for a launcher script, if we want to fix this now, I think we should rather apply the patches. Also note that the data files now need to be installed to /usr/share/teeworlds/data (this is more consistent with the usage of the "data" directory in PWD), and this change should be needed with the next version anyway.