Format
The plug-in architecture takes advantage of the Macintosh resource fork, and a plug-in is composed of multiple resources, most of which are graphical or textual in nature. Each aspect of an Escape Velocity game (including the space ships, graphics for various animated items, missions, planets, and description texts for different items) is described by a different type of resource.
A special file type that ‘flattens’ these resources (with the file extension .rez) is used by the Windows version of EV Nova. To distinguish them from this new format, the traditional resource fork-based plug-ins are sometimes referred to by their Macintosh type code Npïf or, especially among Windows users, by the extension .rsrc which they are given by some Windows-based expansion tools.
Neither version of EV Nova can use the other’s format without conversion. The Windows version includes an Npïf-to-.rez converter, which is a common source of confusion to new users. The Macintosh version does not include a converter, but third-party utilities are available to convert in both directions. Converting .rez plug-ins to Npïf on Windows is not possible, since resource forks cannot exist on Windows; this is, in fact, why the .rez format was originally required.
Read more about this topic: Plug-in (Escape Velocity)