The last of my five "Usborne engine" text adventures turned out to be a sequel to the fourth one, Dark Arts. I had no memory of this fact until revisting the lot of them in 2015, but since their plots aren't too important overall I can see how it would be easy to forget.
In Demon's Keep I shrug off the last vestiges of Scott Adams-style presentation; I no longer clear the screen after every move. In the style of an Infocom game, new prose just appears after the old, though there's no scrollback of your play history. I don't know if I'd ever seen such a thing as scrollback in 1990.
Dark Arts had pushed at the size and RAM limits for a BASIC program. Demon's Keep went a little bit over them, so I split its programs and phases up as much as possible. The game opens by decompressing the graphic title page and playing some Electric Duet music, a transcription of Bach by Paul Lutus. A second program loads the game's database content into memory, then makes way for the game code itself, the third program. A fourth program handles player death and the funeral music I wrote.
I don't know why this game never stuck in my head as much as Dark Arts. It has more sophisticated content — more objects have multiple uses or interact with other objects, and one NPC moves around. And there are some images I particularly like, like the little phantoms and the giant chess board.
I do note that this was the last straight text adventure I wrote for the Apple II from the ground up. It's possible I was simply growing tired of the amount of work involved in each one, and each one was inevitably larger than its predecessor as I tried to outdo my past efforts. Some evidence for my "getting tired" theory is the fact that while I was digging out the notes for these games, I found a map and complete set of notes for another adventure game called Dreadkeep (would I really have made a game with so similar a name?). And I never even started programming that one.
Below are my design notes for Demon's Keep. Click any thumbnail to view a full size scan of that page.
wade_clarke_5_adventures.zip (Contains wade_clarke_5_adventures.dsk)