Games Oh well, bloody hell. The Hitchhikers Guide To The Galaxy text adventure was released across multiple platforms back in 1984 and the key element was that large chunks of the text were written by Douglas Adams and a proportion of that was whole new material. But he also guided the making of the game, helped with some of the puzzles and it's as close to being in the novel or radio series as its possible to be.
There have been multiple versions of the game available since then produced as interactive online experiences (all linked from the Wikipedia page here) but up until now, it's been impossible, as far as I know, to know exactly what Douglas Adams's input was on the game. Until now.
As part of his project to scan everything in existence, Jason Scott of the Internet Archive was given access to Infocom's archive which includes folders containing material pertaining to each of the games which includes The Hitchhiker's Guide.
Which means at this link there's a file containing all of the material pertaining to the making of the game, including Douglas's letters and notes on the game, maps, interviews, adverts, articles, a trove. Wow.