From An Elegy for the Multimedia CD-ROM Stars:

The Codescope, from Corbis's Leonardo da Vinci CD-ROM
The Codescope, from Corbis’s Leonardo da Vinci CD-ROM

The most remarkable innovation by the producers of this CD-ROM was a viewer that allowed readers to peruse Leonardo’s manuscript in 1) the original mirror-script Italian, 2) a reversed “normal” view, 3) a transcription of the original Italian, 4) a modern English translation.