One of the panels at Eastercon (and my mind has gone blank on which it was) mentioned Rob Holdstock's novella which accompanied the computer game Elite.
sbisson has found it on a web site belonging to Ian Bell, one of the creators of Elite:
http://t.co/NAdlyXXxThe site also includes links to versions of Elite for a wide range of platforms
http://www.iancgbell.clara.net/elite/index.htm