Just found this.
Our glorious state broadcaster The BBC has uncovered - updated - re-written - and published the original text adventure game for
Hitchhiker's Guide to the Galaxy as a flash app
I had the original game back in the 80's, it came with a genuine pair of peril sensitive sunglasses. I think mine were broken as they were permanently black.
The original was purely text, the new version is the same, but they've built a nice 80's style gui with a few new features.
If you have (or create) a BBC account the game can save your progress so you can restore later. Useful as it still tries to kill you at every opportunity, just as the original did.
Vogon poetry anyone?