Hi the first think I do now is to get in the lua folder
find where you have install the CorsixTH
mine and the default is
C:\Program Files\CorsixTH\Lua\languages
then take open the notepad text programme and open the lanquage you know
"save as" for example Russian.lua and hit the unicode UTP-8
when you do this may be will save it as Russian.lua.txt
close the notepad and rename the file!! to Russian.lua
then open it again!!!
and then do it again to have the english version or the lanquage you that you prefer , open and work!!

I think you get it!!
if you have any problems tell us!!
Try to translate first the word "RESTART" from the menu!!
and see if can read it right , I have the same problem and I had try different fonts!!
pls tell us your progress !!
Jim from Greece
