Mutant Spiders

(The original cassette cover - read on whilst it's loading and then come back here...)

The 'Mutant Spiders' story begins in early 1983.

I had owned a BBC model 'B' microcomputer for about a year, and had become familiar with its powerful high-level BBC BASIC language.
The next step was to tackle the low-level machine language, known as 'assembler'. It is more difficult, and time-consuming, to write assembler programs but the advantage is that they execute much faster than the equivalent BASIC.

As a learning exercise I decided to write a computer game.

Computer game programs use all of a machine's resources - graphics, sound, real-time input, logic, data-manipulation, etc. - and are fun to design and write.
Games often have to be written in an assembler language as BASIC is simply too slow and inadequate.

I bought two books to help me; 'Assembly Language Programming for the BBC Microcomputer' by Ian Birnbaum (a bit dry, but thorough), and a book on assembler games programming by Jonathon Griffiths (who wrote some of Acornsoft's games such as 'Snapper'), from where I got a useful 'sprite' display routine.

I didn't want to create anything too esoteric, but also didn't want to produce an exact copy of an existing arcade-type game.

I chose to implement a simple Space Invaders type game (i.e. left/right/fire) but make the 'invaders' a bit more interesting. I have a phobia about spiders, so lets make those b*st*rds into arachnids.
Eight legs seemed a tall order to program, so I'll give 'em three instead. AND we'll have those three legs turn into weapons that rain down on the hapless player! That makes them mutants doesn't it?
You can just guess how many long hours of mental gymnastics it took me to come up with a title for my game from all this, can't you?

The game took about 4 months to write. This may sound a long time... and it was!

Games for the BBC micro were of a pretty variable standard. Some of the best ones were produced by 'Acornsoft' and 'Superior Software'.
I sent off 'Mutant Spiders' to 'Superior' and they agreed to market the game in their budget (i.e. 'mediocre') range, for £6.95.

"This is it", I thought, "my fortune at last".
Fast Cars and Loose Women should soon follow!

The game didn't exactly make my fortune. I probably earned about £40 in royalty cheques from it over the next year or so.
It was, to my knowledge, never reviewed (which might actually have been a good thing).

But to be honest I didn't mind that much. I knew it was a rather pedestrian shoot-em-up, but it had featured in a full-page advert in the July 1984 issue of Acorn User magazine (page 91!), which was enough to make me quite happy enough, thank you.

(click on image for full-size version : 177Kb)

Roll on the clock to modern times. I'd long-since sold off my BBC computer and all it's games. I even lost track of the original source code for 'Spiders'.
I had, however, kept my one and only commercial copy of the game (on cassette tape) that 'Superior Software' had sent me.

There has been a recent resurgence of interest in the earlier days of computing (the days before windows, mice and hard disk drives). Many of the older machines have been 'emulated' - i.e. software programs written to run on fast modern computers that emulate the look, feel and functionality of the original machines. There are a few out there for the BBC computer, but many are half-finished and bug-ridden.
However, by far the best of these is a fine piece of software called PCBBC, which can successfully run many (if not all) programs ever written for the BBC microcomputer at the original speed on a modest-spec PC.

I had a desire to see my game running again, perhaps on my own PC running an emulator.

Programs on cassette tape (as mine was) are recorded as a rapid series of high/low frequencies, each representing a single bit. The BBC machine processes files at 1200 'baud', or bits per second.
Normally these sounds would be played into a real BBC micro and the files re-created by the machine. However, none of the emulators allow this as they all use a Disk Filing System (aka DFS) to maintain files - quite understandably too as tape-based file access is a real pain. Remember that 1200 'baud' translates to about 150 bytes (or characters) per second, which by today's standards is a hideously slow rate of data transfer.

I got down my old tape copy of the game and recorded the sound files into my PC and on to WAV files, at 44 kHz.
I used a cunning utility called BBCTAPE to re-create the original three loadable files from the WAVs, and then another utility called BBCIM to create a single disk image holding them all.
I placed the disk image into the PCBBC diskimg directory and attempted to run the game. The title screens all loaded but the game wouldn't run.

After much head-scratching I realised that the DFS was occupying the same storage area inside the machine that the game uses.
Because I had written the game on a tape-based BBC machine there are various areas of RAM storage available which I had used to hold non-relocatable program data and code. The DFS, however, also uses this same space for its work area - and you can't have two programs occupying the same location at the same time.

At this point I contacted the author of PCBBC, Stuart McConnachie, for his advice. He kindly re-coded the data-loading logic for me allowing it to work with disk-based systems and enabling the game to be seen in its original glory.

And now you can see it too:-

There is also a !BOOT file for those who wish to boot-up the game directly.
All you need to do is load the disk image in DRIVE 0 and then SHIFT/BREAK (or SHIFT/F12 on PCBBC) to run the game.

After all these years I still think the game's fun to play. OK it's not Quake, but it's not too bad when you consider its 8-bit origin.

Many thanks again to Stuart M. for his help, and allow me to thoroughly recommend his PCBBC software emulator - see his site for details (hyperlink within instructions above).

There is also an excellent source of general BBC information at The BBC Lives! website.

Some more screenshots from the game.....