| ★ AMSTRAD CPC ★ GAMESLIST ★ BMX KIDZ (c) SILVERBIRD/GIGGLYWURX ★ |
Amstrad Computer User |
Christian Pennycate rests successfully on his laurels after being given just one month to convert a game to the CPC FOR a first release, my conversion of BMX Kidz for the Spectrum hit the jackpot. There is no rest for the wicked, however, and when Colin Fuidge, the Silverbird supremo, offered me a further conversion of the game, this time for the CPC, who was I to refuse? No sooner said than done, my trusty Mont Blanc fountain pen was whipped out faster than a 68000 on speed and was put to the dotted line. Due to me being new to big Al's mighty machine, a little shopping was called for. The recipe chosen to develop BMX Kidz had the following ingredients: A few CPC 6128s, one Maxam assembler rom, one Advanced Art Studio and mouse, one DMP scratcher. Bright and early one Monday morning I called a team meeting - the team being the Zeit Corporation, myself on code and Alex Smith on graphics - to sort out the specifications and draw up a timetable. At first we thought we could download the Spectrum graphics and modify them to take advantage of Arnold's superior facilities. But although both the Spec and the CPC use 3in drives, different disc formats have been adopted. A whole day was wasted battling through the firmware manual to find an elusive address in that infamous jump block so that we could access the Plus 3's disc sectors and extract the graphics codes. Having got that far, we then discovered how the CPC's rectangular Mode 0 pixels had stretched the graphics, giving them the appearance of having been through a mangle. So much for modification, the graphics would have to be totally redone. "There there, Alex", I consoled him. "You'll have them done in two shakes of a mouse's tail." We agreed on sizes and protocols for the sprites and backgrounds and Alex went away, leaving me to get on with the business of persuading the Amstrad that it, too, could ride a BMX, just like the CBM64 and the Spectrum. Choices The first choice I had to make was between a hardware scrolled or a software scrolled playing area. The latter would have meant the use of a work area and kissing goodbye to half the available memory. Since the graphics alone occupied some 28k, this would have left precious little space for my code. The answer lay in offsets, which forced me to work in a modulo 2048 environment. This not only affected the generation of background graphics but also that of sprite placement. Which brings me quite nicely to the bane of every programmer's life, the raster. Sprites Placing a sprite is not just a case of shoving some pixelly perfect graphic on the screen. No sireee, the background must be restored as well. Writing directly to the screen means that all changes must take place without the raster disturbing it. Otherwise the sprites will flicker. The bikes and pickups themselves are 12 x 16 pixels in size and are managed by a stack manipulation routine. With 66,000 clock cycles available between raster interrupts, I found my sprite routine could only handle six sprites on screen without inducing flicker. And because the hardware scroll affects the whole of the screen it was also necessary to restore the score line in order to keep it stationary. Meanwhile Alex had been busying himself with drawing the sprites. These had to be redone due to a mix-up over the palette. But he turned this setback to our advantage, and amended them to make the wheels rotate. Then he started on the backgrounds. These took about a fortnight compared with a week for the sprites. That done, it was time to do the ramps. They were originally going to be twice as wide as they are now, but by that time memory was starting to run short, and we wouldn't want to deprive you of a front panel now, would we? Not being one to stop a man while he's working, I let Alex get on with the job of coding up the level data - the sequence of ramps and background graphics. As they were loosely copied from the Spectrum, they only took about three days to design and debug. Another few days were spent listening to the playtesters'comments and modifying the tracks until just four weeks and three days after signing, the day of judgement arrived. The game In BMX Kidz you have to race over five undulating tracks, competing against three other kidz, performing stunts and wheelies as you go. And as if that wasn't enough, the whole thing is against the clock. Pedalling is thirsty work, and to keep your strength up you must ride through giant size cans of Jump Cola. Moreover, your wheels are not that strong and a bad landing or collision with the other kidz will cause some of your spokes to break, necessitating replacement. This is achieved by riding into larger-than-life sized wheels. To pass on to the next level you must perform all the stunts required of you in the time allowed, and pass the finish line in first place. Judgement day As I was in bed recovering from 72 hours of non-stop coding, it was left to Alex to go down to Silverbird's offices in New Oxford Street to find out what the CBM progger Gl-Jo thought of it. Much to our relief he liked it and only ordered us to make a few minor alterations. That took us a couple of days and then the game was ready to go to be mastered. A few days later we learnt that the masterer couldn't master our master because it was, smiles modestly, over protected. Sigh. There's no rest for the wicked. However I'm nothing if not wicked, and when Colin Fuidge offered me another contract, this time for a jumpy little game entitled Scuba Kidz, who was I to refuse? BMX Kidz was programmed for the CPC by the Zeit Corporation. It will be released next year on a £1.99 compilation tape of three Silverbird budget games. ACU #8810
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Page créée en 248 millisecondes et consultée 2364 fois L'Amstrad CPC est une machine 8 bits à base d'un Z80 à 4MHz. Le premier de la gamme fut le CPC 464 en 1984, équipé d'un lecteur de cassettes intégré il se plaçait en concurrent du Commodore C64 beaucoup plus compliqué à utiliser et plus cher. Ce fut un réel succès et sorti cette même années le CPC 664 équipé d'un lecteur de disquettes trois pouces intégré. Sa vie fut de courte durée puisqu'en 1985 il fut remplacé par le CPC 6128 qui était plus compact, plus soigné et surtout qui avait 128Ko de RAM au lieu de 64Ko. |
