It started with being blown away. The swarms of enemies, the exhilarating freedom of flight, the screen-filling explosions, the aural assault, the daunting array of controls... Defender left most who first encountered it aghast. Archer Maclean shared the same feelings of awe as his fellow arcade-goers, except he wasn’t content with just playing. He wanted to make his own.
“It was a time before any games programmer ever thought about the legalities of looking at an arcade games and wanting to write their own interpretation,” Maclean explains with a wry smile. “You saw something you liked in the arcade and tried to do it at home. Of course I was influenced by Defender, Stargate, Scramble and half a dozen other sideways shooters. Dropzone was a combination of rules from those early games, even its ‘Trailer wave’ was mimicking part of Robotron. But trying to get all that stuff flying about on the screen with an 8bit processor running at 1mhz or so... it was a question of how.” Maclean knew the limitations of what lay beneath the plastic shells of those early home computers. As a teenager in the late ‘70s, he had built assorted homebrew machines and earned some handy beer money constructing NASCOM computers for a local electronics firm. He’d grasped the basics of machine code and produced some simple clones of Space Invaders and Breakout, but the smooth scrolling and frenetic action of Defender remained frustratingly out of reach.
Then Maclean saw the Atari home computers and suddenly anything seemed possible. “I was at an electronics show at the Ally Pally in London in 1979. I was there with the electronics company I was working for, and Ingersoll, who had the franchise to sell Atari computers in the UK, had the stand directly opposite. I saw Star Raiders and it just blew me away. How could it throw that amount of pixels around on the 6502? How could it shift graphics around that fast and detect hits with that much happening? Something very special was happening. I made it my mission to find out what.”
Enthused, Maclean travelled toa Silica Shop in Kent to collect an Atari 800 on the day it officially arrived on England’s shores. Yet even the most intrepid of explorers is in need of a map, and he had heard talk of just such a fabled parchment. De Re Atari, a handbook produced by Chris Crawford and half a dozen other significant engineers at Atari HQ in California, seemed to be the mystical tome that would reveal the machine’s inner treasures.
“It sounded like it was the secret Tibetan Book of the Dead, or something,” laughs Maclean. “I had to get hold of it and ended up paying for a photocopy to be sent from the States. A big, fat three inches of paper. Reading it was like a religious experience. I’d found my Holy Grail! Suddenly, the cloak was lifted and all the magical tricks you could do with the machine were laid bare.”
The first revelation was discovering the programmable video chip, called ANTIC, complete with its own instruction set. Sprites – or player-missile graphics as Atari dubbed them – could be sent scurrying in front off, or behind, a bit-mapped screen. The hardware could handle all the collision detection in the heat of battle. Scrolling was no longer a juddering chore, as the chip could simply be told where to open its window on this hostile world.
“The Atari screen was generally 40 characters wide, equating to 160 pixels, and the Dropzone planetscape was a long strip of memory 255 characters wide. I could just tell the video chip ‘start here’ in one instruction and suddenly it could affect the entire displayed image but without having to re-plot entire chunks of the imagery. And it could do it to the pixel for smooth scrolling! The Atari hardware was what made Dropzone work. I couldn’t have done it without it.”