In my previous post I wrote about how I'd been running CP/M on a Z80-based single-board computer.

I've been slowly working my way through a bunch of text-based adventure games:

• The Hitchhiker's Guide To The Galaxy
• Zork 1
• Zork 2
• Zork 3

Along the way I remembered how much fun I used to have doing this in my early teens, and decided to write my own text-based adventure.

Since I'm not a masochist I figured I'd write something with only three or four locations, and solicited facebook for ideas. Shortly afterwards a "plot" was created and I started work.

I figured that the very last thing I wanted to be doing was to be parsing text-input with Z80 assembly language, so I hacked up a simple adventure game in C. I figured if I could get the design right that would ease the eventual port to assembly.

I had the realization pretty early that using a table-driven approach would be the best way - using structures to contain the name, description, and function-pointers appropriate to each object for example. In my C implementation I have things that look like this:

{name: "generator",
 desc: "A small generator.",
 use: use_generator,
 use_carried: use_generator_carried,
 get_fn: get_generator,
 drop_fn: drop_generator},

A bit noisy, but simple enough. If an object cannot be picked up, or dropped, the corresponding entries are blank:

{name: "desk",
 desc: "",
 edesc: "The desk looks solid, but old."},

Here we see something that is special, there's no description so the item isn't displayed when you enter a room, or LOOK. Instead the edesc (extended description) is available when you type EXAMINE DESK.

Anyway over a couple of days I hacked up the C-game, then I started work porting it to Z80 assembly. The implementation changed, the easter-eggs were different, but on the whole the two things are the same.

Certainly 99% of the text was recycled across the two implementations.

Anyway in the unlikely event you've got a craving for a text-based adventure game I present to you:

• The Lighthouse Of Doom
  • https://github.com/skx/lighthouse-of-doom/

Tags: cpm, retro, single-board computer, z80 | 6 comments