i doubt they fiddled with the Bndl resource, or poked around in the plist, or dropped it into a hex editor.
its likely that they changed all occurences of '.sav' to '.pog' in the source code.
the 'plist' has no information of use...path,sound, volume levels, fullscreen.
the 'bndl' however is blank, i performed a test in june, the file type for a save game is 'CSsg' (coldstone savegame), i created a brand spanking new icon etc, seeing as the MyGame app, was set to use the Bndl resource, it did not work...another apps icon appeared on the file, as it had hen the game created it. teh problem is that the creator type of the save file is BNOX...no app included with CGE has this creator type, nothing has this creator type so nothing will automatically brand it with its icon.
I changed the creator type to BNOX...still no results.
One such reason is that the resource fork of the save file is blank which would be ccommon of an application that exports files branded with its creator type and a vector graphic icon (resource 'icns')...it does not and i couldn't make it.
the extension however still, no.
to clarify,
as far as changing the actual extension yourself on a per file basis, sure. it won't mind.
as far as changing the icon on a per file basis, get info, click on the icon, copy paste, it won't mind.
but near as i can tell it was left open to do this, but it wasn't completed on both ends, just because its changed in the resources file doesn't mean the engine is prepared to accept it.
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... bwahhaaaaahaaaaaugh fooooolish sammurai.