Invasion of the Body Snatchas!

Invasion of the Body Snatchas!
Developer(s)	Simon Brattel Neil Mottershead
Publisher(s)	Crystal Computing
Platform(s)	ZX Spectrum
Release	1984
Genre(s)	Arcade Shoot 'em up

Invasion of the Body Snatchas! is a ZX Spectrum video game developed and released by Crystal Computing in 1984.

"At last! A version as fast and furious and as frustratingly addictive as the arcade original. Landers, Mutants, Bombers, Pods, Swarmers and much much more combine to produce the ultimate space game!"

The Game

"This is a clone of defender and features Landers, Bombers, Mutants, Swarmers and Pods. There is an excellent radar screen, one you can really use for lining up shots, and spectacular explosion graphics. Sadly unless you own a Fuller Box, the game is totally silent. As usual with Defender games, there is not much colour, but the graphics are fast and smooth."

File:INBSSS.gif

Loading Screen

InGame

Notes

Like many Crystal games (and Design Design games to follow) Invasion seemed at first to be a programming exercise first, and a game second. The game consisted of a custom loader, was blindingly fast to play, and the only sound was courtesy of additional hardware that few ZX gamers owned.

A common feature to Crystal games was the bizarre Hi score table - consisting of many different quotes, and pseudo randomized so a different hi score table could be seen each time the game was loaded. Moreover, entering certain words or phrases would replace the entered phrase with another, usually either an in-joke, or continuation of the comment entered. As an example CRASH magazine criticized the speed of gameplay, so entering in "Invasion of the bodysnatchas" into a later Crystal game - Dark Star - changed the text to a phrase "Too fast for you Crash?"

Authors Notes (Simon Brattel)

There were a couple of things about Body Snatchers (I always hated the spelling 'Snatchas', which Chris Clark insisted upon in order to avoid potential copyright claims) that made it unusual. Firstly it was frame-locked, not an easy thing to accomplish with the hardware available, and secondly all the objects existed independently of the display limitations, so an alien that was off-screen could shoot at you, and you could shoot at it. This was something that was generally true of Design Design games. Note that Body Snatchers was a Design-Design game that was marketed by Crystal Computing.

In order to achieve frame-rate there were some fairly aggressive programming strategies. The objects were drawn using code-fragments rather than having character drawing routines and graphical data, there was some hideous code to undraw objects that used the stack pointer to build a definition of what was displayed on-screen, since there was nowhere near enough time to just clear the whole frame-buffer.

To minimize colour flickering most objects were drawn on 8x8 pixel boundaries and moved in multiples of 8 pixels, this being the minimum size of cell that could be assigned different colours with that display technology, and so objects moved very quickly indeed at 50*8 pixels per second...

There is a cheat code (long forgotten) that puts the game into a mode where the players ship repeatedly explodes, and during some television coverage of a computer trade-fair they used our stand as the backdrop for the report, probably the first time a Design Design game appeared on national television (quite possibly the last time as well, now I come to think of it) and this was what was running on the computer that the reporter was sitting in front of. At the end of the report he turned to the computer and pretended to play the game for a few seconds, which looked pretty silly with the ship doing nothing but exploding... Various members of Crystal Computing were visible in the background during this coverage, being on national television probably meant something to us back then when we were callow student types. All except the programmers, of course, who were off boozing in the bar. That being the only thing worth doing at trade-fairs...

The game was credited to Neil and I, but in practice Neil had very little to do with the game and provided support on the development tool side of things; I suspect Neil would have contributed far more if the game hadn't been so boring, from what I remember of the whole process he really wasn't interested in writing arcade clones. I don't blame him, I pretty well lost interest after I'd proved to my own satisfaction that it could be done at frame-rate, which shows in the game itself - there's very little to recommend it. (Many years later I wrote a follow-up for the PC more or less as an apology for making such a pigs-ear of Body Snatchers).

There are several jokes in the high-scores, some of which have been detailed elsewhere and some of which are sufficiently obscure that they are mercifully lost to time. One that I remember fondly and which I believe has escaped documentation until now is the way the lengths of the lines of text in the high-score table were chosen so that the outline of the right-hand side forms a profile view of Graham's head (Graham Stafford was a founder member of Crystal Computing), with a prominent nose, to which the term beak-like could easily be applied. I was particularly proud of working the word "eye" into the lyrics about where his eye should be... I don't think I ever pointed this joke out to him, and but for the fact I'm twiddling my thumbs writing this while a huge file downloads it would certainly have been forgotten. Ho hum, as Martin Horsley used to say.

Reviews

Reviews can be found in the following magazines....

"Invasion of the Body Snatchas is an essential buy for all arcade fans" Sinclair User

"All in all probably the best version for the Spectrum yet" Crash 69%

"A very enjoyable and addictive game. Highly Recommended" ZX Computing

External links

• Invasion of the Body Snatchas! at SpectrumComputing.co.uk
• Invasion of the Body Snatchas! original source code at Design Design