The Hitchhiker's Guide to the Galaxy is 30 years old. It has a 30th Anniversary Edition which the BBC has put online for free. Bless the BBC.
It's a really terrific implementation of the wonderful original game that arrived from Infocom in 1984 with programming by Douglas Adams (yes, the Douglas Adams) and Steve Meretzky.
This new version is playable right now. We've been playing it, badly. It's brilliant. Go over to this BBC page and get into it yourself.