Spectrum games of the mid-1980s were often drawn in one or two colours, because the machine could hold only two colours in each 8×8 block of the screen and a moving sprite in a second colour made its neighbours change colour too, the problem known as attribute clash. Exolon was bright all over, and its sprites moved smoothly across it. Sinclair User, which put it on the cover in August 1987, said that it “follows the path set by Zynaps in using colour throughout”, and that the clash, “while present, is hardly noticeable”. Its programmer, Raffaele Cecco, explained how he had done it in the same magazine four months later.
Fast facts
- Designer and programmer: Raffaele Cecco, for Hewson Consultants.
- Released: summer 1987 on the ZX Spectrum (48K and 128K), at £7.95; Commodore 64 and Amstrad CPC versions followed.
- Hero animation: Nigel Brownjohn. 128K sound and title tune: Nick Jones.
- Size: 125 screens, in five levels of 25.
- Reviews: CRASH 90%, CRASH Smash; Sinclair User cover game.
- Followed by: Cybernoid (1988), also Cecco’s and Hewson’s.
One soldier, 125 screens
The player is a lone space trooper who walks and jumps from left to right across a hostile planet, one screen at a time, with no turning back. The planet throws out round aliens from birth pods, homing missiles, mines, and hydraulic plungers that punch up from the ground. Against them the trooper carries a blaster for the weaker aliens and laser barriers, grenades for the tougher creatures, gun emplacements and blocking rocks, and a pulse bomb that disrupts the enemy’s security systems. Ammunition is refilled with each life lost and topped up from arsenal boxes.
Walking through a dressing unit puts the trooper in an exoskeleton, with more firepower and protection. It has a cost: finish a level of 25 screens still wearing the suit, and the bravery bonus drops from 10,000 points to 1,000. CRASH’s Mike liked the gun “that fires on two levels at the same time”.
Behind the scenery
Cecco described the game’s making in Sinclair User’s “Background Noise” column in December 1987. He had decided to steer clear of “the complex ‘maps and objects’ type of game” in favour of “a more raunchy, blood ’n guts affair” that anyone could “pick up, play and enjoy” without reading instructions, with “lots of big explosions, over-dramatic death sequences” and “numerous wibbly-wobbly aliens”. He drew the backgrounds before writing any code. The hero was animated by Nigel Brownjohn, who gave him “a wonderful (ten frame) lumbering gait”.
The colour came from a decision about what sprites should do. Cecco had planned for the hero to walk in front of scenery, but unless the whole screen was one colour that would bring attribute clash. So he reversed it: sprites gave way to the colours of the background and appeared to pass behind it. He kept a 768-byte “mask map”, one byte for each of the screen’s 768 character cells. A cell holding 255 let the part of a sprite over it show through; a cell holding 0 hid it. Masking only whole cells was coarse, but he designed the graphics so the edges would not show.
That masking took processor time, so he wrote three sprite routines. The slowest drew the large 24×32-pixel sprites, the hero and the pneumatic hammers, with masking and shifting. A second handled 16×16 sprites. The third, for the swarms of small birth-pod aliens, explosion fragments and missiles, did no masking or shifting at all: their images were stored in memory already shifted to every pixel position. The aliens shared one “alien control module”, in which each type followed a table of movements worked out on graph paper, with a random element added so their patterns could not be learned by heart.
Cecco drew his graphics on an Atari ST, sent them by RS232 cable to a CP/M development system where he assembled the code, and sent the result to the Spectrum to test. That was quicker, he wrote, “than trying to assemble 200K of source file on a hot and bothered Spectrum”. The 128K music was an afterthought. Cecco’s early 48K Spectrum was so quiet he could “barely hear” it, but Andrew Hewson suggested 128K sound and lent him a Plus 2. Nick Jones, a programmer friend and “frustrated musician” who knew the AY sound chip well, wrote the effects and title tune. The game checked the ROM when it started to tell a 48K machine from a 128K one.
Reviews
CRASH made Exolon a Smash at 90%, with 92% for addictive qualities. “Instantly playable and highly addictive,” wrote Robin; “go out and buy it,” wrote Mark. Sinclair User’s verdict was “Superb. The best game for ages. All death and destruction on a ludicrously grand scale.” The Commodore 64 version drew a split verdict from ZZAP!64 in September 1987. One reviewer found it a “rather decent challenge”; another called it “insipid and tedious” and preferred Hewson’s other release that month, Zynaps.
When CRASH reviewed Cecco’s next game in April 1988, its contents page sold it on his name: “Exolon author, Raffaele Cecco, produces his best game ever!” That game was Cybernoid.
Two spells at number 1
CRASH‘s Hotline chart counted readers’ votes, not sales (see Reading the charts). Exolon entered it at number 5 in November 1987 and was 5 again in December. The magazine printed no monthly Hotline in January 1988. In February Exolon was number 1; in March it dropped to 3; in April it was number 1 again, and it was 3 in May and June and 6 in July 1988.
Sources
- CRASH issue 43, August 1987, pp. 14–15: Spectrum review, CRASH Smash (Hewson, £7.95, Raffaele Cecco; the weapons, the exoskeleton and bravery bonus, 125 screens; the reviewers’ comments; 90% overall).
- Sinclair User issue 65, August 1987: cover game and review (“Superb. The best game for ages”; colour “throughout”, 125 levels, the exo-skeleton).
- Raffaele Cecco, “Background Noise”, Sinclair User issue 69, December 1987, p. 111: the making of Exolon (aims, Nigel Brownjohn, the ST and CP/M development system, the mask map, the three sprite routines, the alien control module, the 128K sound by Nick Jones).
- ZZAP!64 issue 29, September 1987, p. 28: Commodore 64 review.
- CRASH issue 51, April 1988: contents page, Cybernoid review.
- CRASH Hotline charts, issues 46–54, November 1987 to July 1988; issue 48, January 1988 (an all-time chart in place of the monthly Hotline).
- CRASH issue 48, January 1988: index of reviews (Exolon, 90%, issue 43).