We added an update today that adds support for the following languages for the full UI, all text, etc.:
- Portuguese (Brazil)
- Russian
- Spanish
- Simplified Chinese
They can be set from the game's properties in your Steam library or it will auto-detect this language if your Steam client is already set to one of the available languages.
As budget allows (sadly our budget is very, very small) we will add more languages as we can afford the translation services.