7. Mission: Asteroid

by Garry Francis of Sydney, Australia



Issue 15

May/Jun 85

Next Article >>

<< Prev Article



Roberta Williams is a country girl whose childhood revolved around fairy tales, magic and fantasy. She read a lot, fantasized a lot and told stories to her friends. Some years later, after getting married and moving to Los Angeles, her husband introduced her to an entirely new form of story telling computer Adventures.

Ken Williams was a programmer on an IBM mainframe and used to bring a terminal home every night. As it happens, the computer had some games on it including the classic Crowther and Woods original Adventure! After playing it at home, Roberta said to herself "Gee, I could do that!". So she designed an Adventure called "Mystery House" and Ken did the programming. It was a fairly simple game inspired by the Agatha Christie novel "Ten Little Indians". It had black and white line drawings and was only available for the Apple, but it was a start.

They formed On-Line Systems (which later became Sierra On-Line) so that they could distribute the game. Before long they released a second game called "Wizard and the Princess". It had full screen, high resolution colour graphics and was heralded as a major breakthrough in Adventures. On-Line's success was now assured.

Over the next couple of years, the number of Adventures increased with each new release seemingly bigger and harder than the previous ones. The one exception was "Mission: Asteroid". This was written as a beginners' Adventure and was accordingly given the number 0. There are now seven in the series, but only the even numbered ones are available for the Atari. Who knows? Maybe the others will one day be translated as well. The full series is listed below.

#0: Mission: Asteroid
#1: Mystery House (not available for Atari)
#2: Wizard and the Princess
#3: Cranston Manor (not available for Atari)
#4: Ulysses and the Golden Fleece
#5: Time Zone (not available for Atari)
#6: The Dark Crystal


We'll take a look at Mission: Asteroid as it's the first in the series, but most of the comments are equally applicable to the whole series. When the game is first booted, the program checks for unformatted sectors on track 3. This results in the dreaded graunch ... graunch ... graunch that I've come to hate in Sierra On-Line's copy protection. I wish they wouldn't do that! Haven't they ever heard of bad sectors and duplicate sectors and short sectors and skewed tracks and...

Anyway, you are then asked to flip the disk to side 2 and press RETURN. When you've done so, a triangle appears along with the message "IF TRIANGLE APPEARS BLUE PRESS THE START KEY. IF IT IS NOT BLUE PRESS THE OPTION KEY." The triangle on my screen could best be described as scunge (which definitely isn't blue), so I pressed the OPTION key. However, I soon realised that I could press the START key and there was absolutely no difference in the pictures. I reasoned that the test was necessary because the game used artifacting. They needed to determine whether the computer had a CTIA or GTIA chip, then the program could compensate so that the colours looked right. However, this only applies if you have an NTSC computer and television (as in the U.S.A). It does not apply to we PAL users in Australia and the United Kingdom, so you can press either key and it doesn't make the slightest difference.

The game then commences and you get your first glimpse of the much acclaimed graphics. What do you think? Terrible aren't they? Apple owners can't be very fussy! The pictures look like they've been drawn by a kindergarten child. To make matters worse, the artifacting mentioned above just doesn't work on PAL televisions. Instead of the glorious technicolor that we're used to on the Atari, we get just two colours black and a horrible yellow that looks like cat vomit.

The screen layout is just like GRAPHICS 8. Most of the screen is devoted to a high resolution picture of your surroundings except for the four lines of text at the bottom. Each time a new picture is drawn, the bell rings from the console speaker. (This also happens with Wizard and the Princess and Ulysses and the Golden Fleece, but The Dark Crystal uses the TV speaker.) If there are more than four lines of text, then the first four lines will be printed and you have to press RETURN to continue with the next four lines. This prevents the text from scrolling under the picture before you get a chance to read it. Unfortunately, no matter how hard you try, you nearly always forget to press RETURN before starting to enter your next command. As a result, you are punished with another repulsive bell, but this time it's three times as long as before. In a short period of time, I got rather annoyed with this to say the least. A reviewer in another magazine was ready to throw a brick through the TV before his family dragged him off screaming. Another resorted to pulling his computer apart and disconnecting the console speaker!

If you're thinking that there must be a less drastic fix, then you're right. Use a paper punch to cut a write protect notch in side A of your Adventure disk and run the program at the end of this column. Hey presto! No more bells! Note that this will void any warranty you may have on your disk, so make sure you are very careful not to make any mistakes. The program has all the instructions you need and is written in such a way that there is no way it will alter your disk unless it is identical to mine. (Try it on any of your other disks if you don't believe me.) If you follow the instructions, you can't go wrong.

At this point, I must give credit to a friend named Peter Bamford. He was the one who originally thought of the fix and passed it on to me. I merely repeated the procedure and wrote the utility to allow any mug to fix his own disks.

Peter began by searching the disk for the bell character, i.e. $FD. Unfortunately, it appeared about a million times. Not only did it appear as data or part of an address, but it also turned out to be a 6502 opcode. Obviously, the search would have to be narrowed down. (Incidentally, don't bother checking track 3, because it is unformatted and will cause your drive to have a seizure.)

He then searched for the sequence $1F, $DO. This is the hardware register CONSOL in LSB, MSB format. Most readers would be familiar with reading this register to see whether a console key is being pressed. It can also be written to to control the movement of the cone in the console speaker. If a sequence such as $8D, $1F, $DO (or STA $DO1F in assembly language) was found, he'd be in luck Unfortunately, no such luck. This was becoming a real Adventure in itself.

He then took a look through the Operating System source listing for a clue and accidentally stumbled across the label BELL in the cross reference map. It turned out to be a subroutine in the display handler that rings the bell. This is where I became involved. The obvious next step was to search the disk for the sequence $20, $0A, $F9 which translates to JSR BELL (or JSR $F90A) in assembly language. This sequence occurred five times. Aha, jackpot! The first occurrence was found at sector $02 byte $31 in Mission: Asteroid and Wizard and the Princess and sector $05 byte $32 in Ulysses and the Golden Fleece. It was used to ring the bell to let you know that you had to turn the disk to side B. I decided to leave this intact.

The second occurrence was at sector $F2 byte $71 in Asteroid and Wizard and sector $E8 byte $71 in Ulysses. This sounded the bell after each picture was drawn. I replaced this with $EA, $EA, $EA which translates to three NOPs in assembly language.

The third, fourth and fifth occurrences were immediately after one another at sector $F3 byte $02 in Asteroid and Wizard and sector $E9 byte $02 in Ulysses. This was the triple length bell that occurs if you forget to press the RETURN key when there is more text to print. I again replaced these with NOPs.

Each disk was modified and tested. The results? Silence. Beautiful silence!

Incidentally, the JSR BELL is an illegal entry point. If the programmers have done it once, then they have probably done it several times. This implies that the Sierra On-Line Adventures may not run on revised Operating Systems such as Revision B, but this shouldn't affect us as Revision B was never issued in a PAL version. XL users will probably need the XL translator disk. If in doubt, try to check that the programs run okay on a system similar to your own before you buy them. I don't think you'll have any trouble, but it's better safe than sorry.

Up until this point, my comments have been very negative. This is not to say that the game is no good. On the contrary. As far as Adventures go, Mission: Asteroid is very good! The aim of the game is to blow up a huge asteroid before it collides with the earth. The game commences at 12:00 noon and the asteroid is estimated to hit the earth at 7:15 P.M. This gives you 7 hours 15 minutes of game time to complete your mission. Each move takes 5 minutes, so you effectively have 87 moves to solve the game. The puzzles are fairly simple and logical, making it ideal for beginners. It is the time element that's the real killer.

Mission: Asteroid also has one of the most intriguing mazes that I've ever encountered. Although the game gives you a route through the middle of it, it is not the most efficient, so you should try mapping the maze to find a better way. It's quite a challenge, but I'd say very few people have bothered. Even the two books of Adventure solutions mentioned below have conveniently left it out!


There are no hints this issue because none of the problems seemed hard enough to warrant them (and I couldn't think of anything particularly clever anyway). It's just a matter of working out what to do, then doing it in the shortest possible time. If you get really desperate, a complete solution can be found in "A Shortcut Through Adventureland" by Jack Cassidy, Pete Katz, Richard Owen Lynn and Sergio Waisman (Datamost) and "The Book of Adventure Games" by Kim Schuette (Arrays,Inc.).

AtariLister - requires Java