Operating SystemI love Linux and Unix. Not everyone uses it or can use it, though. Simple DirectMedia Layer library, and other cross-platform libraries (e.g., libPNG) helps makes most Tux Paint code run anywhere.
ArchitectureLinux and Unix run on various architectures (Intel x86, Alpha, Sparc, PowerPC, etc.), and Windows and Macs run on different chips from each other. Libraries help make supporting them trivial. Endianness was an issue, though.
Language (Human)Spanish translations came first. Coded using C '
#defines. Quickly converted to GNU gettext. Over 15 languages currently supported. Asian and other Unicode language capabilites are ready and waiting!