The answer is simple. Try running all those old classics, like Dark Castle, Beyond Dark Castle, the Fools Errand, and so on, on a Mac without a 9-inch monitor. They don't work. A shrunk image of vMac running System 5.5 vMac is developed by a team of developers around the world.
Source code is available.
The Macintosh version available from this page includes the full source code in the archive. This site is generously sponsored by TVCNet .