If necessary, I think you can actually run old versions of SSW on the Plus and even the SE (down as low as 3.0, which I think was the OS the Plus originally shipped with), so most games requiring those older versions should run on those machines.
However, any lower, and weird things might happen with the hard drive, because those early versions don't understand HFS, if they can even understand what a hard drive is (does the HD20 software work on System 1.0 or 2.0? If so, that would negate this particular problem).
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