Sunday 16 June 2024

The Six Lilies/Le Jeu de Six Lys by Infogrames (1984)

I have made another conversion of a game for the Matra Alice to the TRS-80 MC-10. This game is a computer role-playing game (CRPG). It uses some nice graphics that are made possible by the upgraded graphics chip for the later models of the Alice, which had the same chip as the Thompson 8-bit computers.

Dead-end

There were some pretty creative images, generated using line-drawing techniques developed by the Infogrames programmers.

4-Way Intersection

These graphics are drawn using machine code routines that are loaded along with the BASIC program.  The BASIC program, however, covers combat and other main functions of the game like random item distribution and input, so all I had to do was recreate new room, character and item drawing routines in BASIC. Despite the creativity and variety of the hires images, they all boil down to 3 basic forms: Passages (no distinction between east-west, and north south), 4-way intersections and dead ends. I was able to create a simple room rendering engine using the chunky lowres Semigraphics-4 graphics of the standard MC-10/4K Alice. This engine indicates which directions there are exits (north, south, east or west) in the orientation North-back, West-left, East-right, South-foreground. It didn't require too much memory and was as speedy as the machine language line-drawn artworks of the original. Simple, but they do the trick:

North and South exits ("Guard" spelling now fixed)

4-Way intersection with East and West Exits

In my system, dead-end rooms are just rooms with one exit, but unlike the original, they clearly indicate in which direction the exit is located.  I was able to have enough room for just two extra special rooms. One was the "Web Room" where there always seems to be a spider (a very powerful creature) which must be defeated before approaching the dragon.


I've refined this room graphic a little since taking this screen shot by adding a web string in the upper left corner. I also changed the name of the creature from "Migilus" to "Spider".  I generally moved towards trying to use clearer English equivalent names for monsters when they were apparent.  For example, "Nain" which is French for "gnome," was renamed and given a little red "hat" to evoke the garden gnome clichĂ©, just for fun.  I went through two renderings of the Dragon big baddie, which is double width to all the other creatures.

Chunky original dragon idea

More stylized dragon I chose 

I went with the less chunky dragon, but please let me know if you feel I went the wrong way. I had to work the semigraphics-4 hard to get an interesting variety of monsters to cover the 40 used in the game. Each is meant to evoke the size, ferocity and type of creature from the original artwork, but I did take some liberties. These are the "glyphs" I came up:

Monsters 1-16

Each monster was limited to a 4 by 4 grid of pixels, which due to color clash, must largely be limited to a single color.
Monsters 17-32

Colors can be used to evoke certain kinds of monsters. For example, white is a good colour for undead types. You can see in the above how I was able to sneak in the red cap of the gnome by carefully avoiding color clash between individual 2X2 pixel character blocks.  When the names, which I think were probably loosely based on Latin terms rather than French, were not hard to pronounce and were evocative of something, I left them untranslated. Otherwise, I opted for straightforward English terms for the various types. Their size relative to the player will hopefully indicate that these creatures are of extremely large size and aggressiveness for their species. But not all of them attack when you enter a room. Some are simply cannon fodder, that you must combat to build up your strength and constitution in preparation for fighting the Dragon.  You must figure out which are the most and least dangerous, and start small and work your way up. Otherwise, you are doomed. The food and other items in the dungeon can help you replenish constitution and can raise and lower your intelligence, which also helps with your combat.

Monsters 33-40

If you manage to survive and build your stats to an appropriate level, you can face the dragon (seen above in "split" form).  If you can defeat the dragon, you can make it to the room with the Lily, which you can then take to an appropriate room (which you must find) to win the game.

BUGS

As with many of my conversions, including my last one (WW3) from the Alice, I found some bugs. At least one was potentially game busting depending on your patience. I found that if you picked up and then dropped the sword, you would be granted a larger amount of Constitution points than would be taken away. So if you simply stayed in a room picking up and dropping a sword you could conceivably raise your constitution to whatever level you needed to defeat everything in your path.  It might take some time, but players back in the day would have ruthlessly seized on such bugs to achieve victory, no matter how underhanded such a victory would be. Here is the kind of progression in Constitution you would see from a series of pickups and drops:

234, 244, 239, 249, 242, 252, 247, 257, 266...

It struck me as an inadvertent asymmetry in the GET and DROP routines. Possibly there was some concern that since any action, including dropping an item, also uses a small fraction of Constitution (which is like your "energy level") some restitution was due. But the decimal math was not right for simply offsetting that specific fractional amount. It just seemed to be a mistake. It only effects the sword, since that is the only item that grants an increase in Constitution when you GET and carry it. I fixed it so that the benefits of STR and CON are given and taken to the same level for GETs and DROPs.

A less game-breaking bug is one that affects the reading of scrolls.  It is clearly the case that like most of the items some scrolls are positive and some negative. For example, some vials are poison and some are magically helpful for (STR, INT, or CON).  But the routine to register either positive or negative effects jumped to a line number just after the IF check for deciding whether an item was of the positive or negative type. So all scrolls would simply default to being positive in effect. But given the information messages that are provided when you use the "IN" (Intelligence/Inquiry) command, some of the scrolls are clearly meant to be negative. In general, scrolls and vials that are good provide more benefit compared to the bad effects of negative counterparts, so there is an incentive to be cautiously bold.

In relation to the IN command, it takes a number of intelligence points to use that command, which is obviously meant to be a disincentive from using it too much. But I read in the instructions that this command was only available to those of requisite "high intelligence. " But the game would let you use the IN command without limit and subtract points even into the negative range, which seemed strange. So I added a feature to only allow use of the command if you had Intelligence points above at least zero. Otherwise the message "nothing" is printed.  A player must be careful about using the IN command and should not ignore INT when choosing character stats at the beginning and try to keep them up during the game.
 
Finally, there was a minor quirk in the way the game seeds the random number generator, which resulted in the first game always being the same dungeon arrangement from a cold computer start and game load. This is because the random item/monster distribution routine is called before the "random seed" routine is called in the form of an RND embedded in a "press a key" loop. So I changed this so that you always get a completely unique game for any startup. The program also NEWs itself if you lose, forcing the player to reload-- Part of the incentive to play well, I suppose. I took that feature out, and added a simple re-start prompt at the end. I also added a brief version of the game backstory as part of the intro screens, and a list of the commands. That way, anyone playing the game online can simply figure out what is going on after typing RUN/

If someone from the Alice world would like to fix the bugs I believe are in the original version, I have added REM statements regarding the three main ones discussed above.  The source code (highest number is lates version) can be found here: 


My version of the game can be played online at the Internet Archive:


P.S. Thanks to whoever created the walkthrough map, which can be found online.  It was really helpful.  And to Le FĂ©tiche for his long-play video of the original game:


SPOILER ALERT

The following is a video of the dragon being defeated. It shows where you must go after defeating the dragon to win the game, and the brief animation that your final victory.  For those who don't wish to spoil the game, I recommend playing the game yourself!


Video of a win!




Sunday 31 March 2024

"Castle Adventure" by Dave Trapasso (1981)

This is a type-in text adventure from Computronics magazine, April 1982, which I don't think exists as a playable game anywhere on the Net. It was originally for the TRS-80 Model 1/3, but my version is for the TRS-80 Micro Color Computer:


Here is a walkthrough map:


The magazine scan was very clear. I mostly only had to add carriage returns and fix a few lowercase L's in place of 1s. Otherwise it was just a standard exercise in using my word-wrap routine and reconfiguring (cutting by half) the PRINT@ commands from the Model1/3 screen, which is 63X16 to scale the messages to the MC-10's 32X16 screen. The program has a somewhat unique screen layout with room descriptions and items being printed at the top, response messages in the middle, and commands entered in the bottom two lines. I had to make new clearing routines for these different zones and I bumped the response message area up a line to just below the demarcation line (now a sequence of SG4 characters representing a castle "parapet") between the top description zone and the message zone. This is because some of the messages obviously take multiple lines on the MC-10 and the bottom of the main message area is used for temporary messages like INVentory lists and random messages, such as when the damsel yells for help.

Finally, I added a pixel art title screen to replace the simple REMarks with the authors name and date info. I didn't include the old address info.

The game "CASTLE" can be played at my GameJolt page under the "Text Adventures" menu item. Just select PLAY GAME, then the "Text Adventures" item, then CASTLE from the Cassette menu and type RUN and hit Enter in the main (green) menu screen.

https://gamejolt.com/games/jgmc-10games/339292

Saturday 23 March 2024

"Adventure" by Let's Compute Magazine (March 1991)

I've typed-in a demo text adventure from a UK computer magazine called "Let's Compute." The CPC computer wiki describes the history of this publication as follows:

Let's Compute! was a monthly British magazine that catered for the Electron, BBC Micro, Commodore, Atari ST, Spectrum, Archimedes and Amstrad CPC. The magazine was 99 pence and only lasted 12 issues (August 1990 to July 1991).

It was produced by Database Publications-- with the managing editor being Derek Meakin (from Computing with the Amstrad).The last two issues were published by Europress Publications.

The magazine covered as much as possible in its 48 pages - game reviews, news, cartoons/jokes, reader questions and type-ins. Sometimes the type-ins would specific only to certain platforms, other times they would provide you with the lines to change in order to make it work for your platform.

The text adventure engine/demo program was covered in the magazine's last 5 issues (March-July) 1991. The game as published functions but it's puzzles/storyline were not completed. There was going to be a least one other installment of the series covered but the magazine was cancelled after issue 12.

This loose end struck me as particularly sad because when I typed in the program I discovered quite a nicely programed and flexible text adventure system programmed in BASIC.  It uses DATA statements with a clever system for sensing additions and calculating the number of items and actions being added, and adjusting itself accordingly.  It also uses a complex system of hashing/encoding what happens with new vocabulary, items and actions that is both flexible and efficient.  The result is that the parser is both quick and able to sense unique vocabulary terms, either verbs or nouns, that can trigger appropriate responses even if the user types complex phrases or even sentences.

It seemed a waste that this program should not be preserved for posterity.  I suspect that I wasn't able to find any evidence that it had been preserved as a running program anywhere on the Net because 1991 was a bit late for type-in games and the timeframe of the computer systems the magazine was directed at were already well into the period of the dominance of commercially produced software. I suspect very few people using them would have wanted to type in and preserve type-in games, especially ones that were never fully completed.

So  I have completed the story as best I could from the clues and the layout of the items provided in the source code and also from the discussion in the accompanying articles. I feel pretty confident that I have recreated the demo adventure storyline that the author or authors were aiming at and likely to have produced in the final article. And just for my own fun in TRS-80 MC-10 programming I added a fancy title page using semi-graphics-4 characters.

The magazine article begins "We're off on the road to Adventure."  It's a simple space adventure somewhat akin Lance Micklus' 1979 Dog Star Adventure.  There are a few tricky puzzles and only a few possibilities for insta-death. No specific author is identified in the articles from what I have read (perhaps they are mentioned elsewhere in the magazine). The version I made is for Micro Color BASIC on the TRS-80 MC-10 but the article claims the program should work with only a few minor changes on the BBC, Archimedes, Amiga and PC (GW-Basic), but that it will not work on the C64/128 or Spectrum.  However, I can see no reason why it shouldn't work on the C64/128. I suspect the intensive use of string handling and string handling commands (MID$, LEFT$, RIGHT$) used in the program might be difficult to translate to Spectrum BASIC, which treats strings as string arrays instead of using string functions to manipulate them. The C64 omision might simply have been due to its shorter line length (80 characters), which might have required some extensive editing of long lines to reconfigure for the C64.

The game can be be played by selecting "Play" on my GameJolt page, then "8-Bit BASIC Text Adventures" and then choosing LCADVENT from the Cassette menu.  Finally, type RUN and hit ENTER in the emulator's main green screen:

https://gamejolt.com/games/jgmc-10games/339292


"Minidam" by Christian Garaud (1985)

This program is a "solitaire" logic puzzle game. The goal is to transpose the red pegs and blue to finish with the red pegs on the right and the blue pegs on the left. A peg can only move diagonally in the direction it is meant to travel, towards an empty space or jump over a peg to reach a space that is empty. You can start with any colour that you want. To move a peg, just type box number in which it is located. If you are stuck, type 99 to restart.

Published in the French language magazine Micro 7, April 1985.  I translated the French prompts and ported to the code to Micro Colour BASIC.  The game was originally for the ZX Spectrum 8-bit computer.

Not sure if this puzzle even works.  But it struck me as an interesting piece of code to get working, from a old computer magazine that I had never heard of before.

I also typed in another program called "Testamour" (TSTAMOUR). It is credited to the editorial team of Micro 7.  It's meant to test the reader's knowledge of BASIC. If they could figure out what was going on, then they would be able to respond in a way that they would get rewarded with an image being printed on the screen. Perhaps the answer of what the program did would have been revealed in the following month's edition of the magazine for those who didn't understand BASIC well enough to figure out the trick for getting the image to display.

I know Steve Bjork had mixed feelings about the MC-10, but as an MC-10er I have nothing but the deepest respect for him. His programming skills were an inspiration to me as young programmer. Allen Huffman recently sent me some old BASIC code of Steve's. I have ported his perpetual calendar source. Now he is a contributor to the MC-10 program library. Thanks so much Steve!

Finally, here is a slight update to an old program from way back that I typed-in called XMAS.  It is from the Coco.  But the program only used to blink red lights by using RESET. But now I have it cycle through multiple colours.


Tuesday 20 February 2024

"Haunted House" by Tandy (1979): A Narrative Update

This is a classic text adventure first sold for the TRS-80 Model 1 in 1979 by Tandy. It is a little unclear who the actual author was, but the game was originally a machine language game in two parts, which was able to be played on an original 4K TRS-80. More info on the game can be found on numerous sites, such as the following very helpful homage site:

https://www.figmentfly.com/hauntedhouse/hauntedhouse.html

Now it is available for the TRS-80 MC-10 because Donald Foster ported the game to QB64 BASIC and posted his source online. I just had to add line numbers (instead of subroutine titles). I can't recall now or locate where I first spotted his source, but it was attached to a post in one of the innumerable retrocomputing forums that I visit.  He has my thanks. If I recall correctly, his post asked folks to try out his port and report any bugs. I think I might have overcome some minor ones and some limitations in game logic in a few places, which I can't recall now. But there was one major bug I do recall. The 4th "chief" ghost was supposed to be "immune" to the attacks of the sword, but I think instead there was the same message printed about "killing" the ghost.  But the ghost would still be there regardless of the message. I noticed this because published walkthroughs of the game kept mentioning how the main ghost was "immune" to your attacks.

This got me going on a kick to make some more changes to the game. I added an intro screen in semigraphics-4 mode of a creepy old house. I also made some corrections to the intro text that Foster had added (from the manual I presume). Thanks to some folks who posted some comments on my first video about the game I was able to correct some spelling mistakes and typos. 

I've now made some substantial additions and a few subtle changes to the messages and the outcomes to try to create what I feel is a more coherent narrative for this classic. Even in the original game it was apparent that there were two warring metaphysical factions at work in the house. I have worked to clarify and highlight this tension. Each faction is contending with the other as a result of a terrible wrong that has trapped both in a seemingly interminable struggle. 


-- Can you figure out which is on the side of right?  Can you help right a historic wrong and bring resolution to a lost soul?  It all depends on you!


I have added many messages that hint at this refined narrative to allow the player a richer more standard text adventure experience than the original spare 4K version could provide. For example, Jason Dyer of the Renga in Blue text adventure blog series expressed frustration with the lack of interactivity with the BUCKET object regarding the flames in the first floor master bedroom:

https://bluerenga.blog/2016/09/21/haunted-house-finished/

The bucket it turns out is a complete red herring because the fire is an illusion. But now with my changes you can at least try to use it and get some response instead of the original game's standard "I don't understand."

The player can now "examine" things and get some narrative hints at what might have occurred in the house to create the metaphysical deadlock. As noted above, the original narrative hints at some struggle between spirits-- malevolent versus benign. The knife doesn't want you to read the scroll for example. But the scroll points to a possibility of escape. The fire seems aimed at preventing you from getting to the room with the hole that will take you to the second floor, but if you get there the rope uncoils and allows you to go up. The three upstairs ghosts in the main rooms block your way, but a magic sword is left that allows you to vanquish them. Behind one of those ghosts is another who, if you get to him only lets you pass to the final room if you relinquish the weapon. I added the necessity of also "killing" (i.e. dispatching to hell) all 3 of the obstructing ghosts.

I made this addition because otherwise there appears to be no function for killing the other two ghosts, since they don't obstruct you from getting to the 4th ghost. And I take it as given that these are the three malevolent spirits of the house and that the 4th is benevolent (i.e. fundamentally non-violent) and that there is a issue of justice at stake. The intro mentions "a visitor." My take on the story is that the visitor was an innocent victim of the three sinister and grasping McDaniels who had made vast profits off of illegal hooch manufacture during prohibition. I've added clues that hint at this narrative that you can find by using the added "examine" command. For example, one clue you don't see in my walkthrough video above is that if you EXAMINE COINS you will see they are minted in 1932, which was a year before the end of prohibition. 

I also changed the "suit of armour," which prevents you from getting to the key in the servant quarters, to a "spectral hound". The suit of armour seems out of keeping with the North American setting I am assuming for the house. If one assumes the knife is in the command of the evil McDaniel spirits, then the possession of the crumpled paper talisman with "Plugh" on it, is imbued with the power of the good spirt. Even in the original game you must be carrying that paper to be able to get hold of the floating knife. If you don't have the paper, you can't get the knife.  But if you do get the knife then you can also scare the spectral hound/suit of armour. My take on this is that the knife of the McDaniels was often used to harm their old guard dog. So the control of that knife can actually be used to subvert their manipulation of the spectral dog to protect the servant quarters. If you get past the dog you can now also find bottles hinting at the source of the McDaniel's ill-gotten wealth.

So I am of the mind that somehow in around 1932 a federal agent by the name of Plugh was investigating the "hooch magnet" McDaniels when somehow he ran afoul of the murderous clan. They killed him, but somehow he was able to strike back, either metaphysically after his death, or before his death in some way that brought about their end as well, and perhaps inadvertently the end of their poor maltreated dog too. I'm thinking a gas leak or a series of fomented mishaps. Their house was obviously booby trapped to the hilt to prevent theft of their vast wealth, which can now be seen in the final room. Perhaps even Plugh was tempted by that wealth and the possibility of making off with it, which helped bring about his end. This might explain the somewhat cryptic/ambivalent/poetic clue scratched on the sign in the final room. I have added the treasure at the end to allow for this reimagined scenario. Can you maintain your honour and escape like Plugh perhaps did not?  Can his failure to rise to the challenge of this temptation explain why he was consigned to his spectral existence-- to atone? Can you rise to the challenge?  The introduction hints at what you must do.

Enjoy.

Jim Gerrie, (c) 2024.

"HAUNTTRS" can be played online here (at least for a short while): https://archive.org/details/@james_gerrie


ADDENDUM

I've made a few more changes and additions in keeping with my new narrative.  I changed the paper at the beginning to an FBI badge with "Plugh" on the back of it, and hidden it under the front mat. I've also added a reaction of the benign ghost if you drop the badge in front of it.  To allow for this, I've added the ability to "wear badge", which will allow the badge to be carried with you up the rope. I might as well go whole hog on altering the game since there's no point in just recreating the original.  There are many ways for folks to play the pristine original if they really want to. Here's a video with the main changes demonstrated-- and a "speed playthrough" to a win-- SPOILER ALERT!



ADDENDUM TO ADDENDUM

I made some more changes. I added some randomness to the location of the rope. I added much more descriptive content to be EXAMINEd. I added the ability to move objects around and drop them in other places and then pick them up again.  I added another puzzle regarding the badge. Now you must have it for the sword to appear. There is not much more that can be added.  Sadly I'm getting close to the max 20K now.  So hopefully, this will be my last addendum.  The game should now at least be equivalent in game play to your average 16K 8-bit BASIC text adventure.  Abysmal, but better than a two meagre 4K games. My task is complete.  I feel I have taken a classic game that was an introduction to many, but sadly somewhat wanting because of the strictures of the classic trinity 8-bit computer it was designed for, and rounded out its very suggestive but minimalist storyline.

Monday 1 January 2024

"Dungeon" by Brian Sawyer (1979)


This is a port of the classic PET "Rogue-like" game (before Rogue) "Dungeon" to the TRS-80 MC-10. I found an unfinished part in it that would have allowed the player to have a double distance "fog of war" view instead of the single space view immediately around the player's position. The "S" key was assigned to the function and it would have cost -2 HP. In fact, I think the -2 part of the function works when you hit S, but the full expanded view routine doesn't seem to have been implemented. See lines 610 and 1310 in the source that I worked from:

600 K=-40:J=3:M=40:R=3:GN=0
610 IFSM=1THENK=-80:J=5:M=80:R=4:SM=0
620 O=L-32767-R
630 IFO+32811>33768THENM=0

This is the beginning of the "fog of war" reveal routine. The SM variable is a switch that if activated in the key input routine causes an alteration of variables to create different offsets for the reveal box around the player. But not all these variables are actually used in the subsequent nested FOR/NEXTs used to display the spaces around the character.  I think Sawyer realized that an odd number would be needed for the routine to actually be centered on the character, which would require a 5 X 5 character space box around the player character instead of an originally planned 4.  Also, this would require some error checking as the routine moved past the edge of the screen in the bottom right and top left.  A vestige of that can be seen in line 630 where a check is made to see whether the offset takes the view outside of screen memory at the bottom right.  

Here is the code that was meant to switch the mode on:

1310 IFL$="S"THENSM=1:HP=HP-2

My guess is that Sawyer realized what a daunting task getting the routine working would be (a bounds check also for the top left, for example) and that the game was playing just fine without it. So he just left it half implemented and carried on. It is not uncommon to find such unfinished bits and pieces in old BASIC games. I think there were other unused variables that I removed from this game and untold others in other games. They are the vestiges of the unwieldy editors that one had to use back in the day.  It was impossible to simply see the code whole and to be able to do quick searches. LISTing and then pausing the display as the lines sped past meant that many false starts would simply be left in place if they didn't impede program execution. Today I like to clean these things up, as they can help smooth out and speed up game play.  I recognize that there is a loss of fidelity with the original, which is why I try to document such modifications. But my love of these programs means I like to see them run as best they can.

To that end I also added a feature to continue with another dungeon if you get all the gold on a screen.  The game as it was would simply end in the same way as when you die. It would reveal the map and prompt for a replay. It didn't display a win message.  However, it seemed simple to preserve the player's basic stats of Hit Points, Experience and Gold Pieces and then generate a new map for the player to continue their quest. This will be extremely difficult as the monsters ramp up according to your own HP modified by their own intrinsic level of ferocity.  In fact, it might be a good strategy to simply bleed off HP down to a level that is easier to manage.

I also added a "bloodstain" which shows where you were killed on the map. It's just a red block, but it helps differentiate an end from death versus completing a level. I also added messages "You have found all the gold" and an alternate prompt "Continue to next level?" if you complete the map. Here's a video of a test of an early version of this feature:


I also added some sounds, such as when you find gold or are killed, since the MC-10 is a slightly more advanced machine than the soundless classic "trinity."  And I added some instructions to the title screen about the keys used in the game.

Hit Points Oddity Fixed?

There's an oddity about one of the keys. There seems to be no limit to the player's ability to press R (the 5 key in the original game) to "rest" and gain Hit Points. The only disincentive seems to be the time taken waiting for the screen update.

1290 IFA=ASC("5")THENHP=HP+1+SQR(EX/HP)

The use of the SQR function and a division of Experience by Hit Points scales the function down (I think) as you increase the number of HP, so the speed of increase will decrease as you add HP.  This means you will have to waste more time pressing the R key.  And you also will simply have to fight tougher monsters as you add HP as HP is one of the factors determining the stats of the monster you face.  So there is some mathematical alchemy of hitting the right spot of building strength in relation to experience that might be useful for game play. I will have to examine the code more closely and discuss this issue with my mathematically adept son next time he comes home. If he has any insights, I'll add them here.

But as I tested the game I realized that using the Rest function in combination with the "walk-through-walls" spell gave a pretty ironclad way to defeat the game. You just have to run away from monsters after you get the report of their HP and then build HP using the Rest function until you are equal or better than them. Then I realized I could even do this from the safety of being inside the walls!  So, as soon as I spotted a monster, I would just fade into the nearest wall and start hitting R. Then I would reemerge and kick the monster's butt. This seemed unfair and kind of dull once I'd figured it out.  So I just modified my version to prevent Resting while inside walls. And as further incentive, if you try to do this, you lose the standard amount of HP used for regular movement. I thought this made sense.  After all, you are casting and maintaining a powerful spell while travelling inside walls.  Now, at least you must use HP to travel and then risk emerging into areas to rest that may be inhabited by other denizens of the dungeon. A little more resource management and path planning skills will be needed.

Finally, I had to take all the fancy string declaration used in the original PET version to clear a space in high memory where the dungeon can be safely POKEd before being revealed to the screen by the Fog of War function.  Robin from 8-bit Show and Tell has a nice video documenting a bug that affects this function between early and later versions of PET BASIC.  This video is what made me aware of this classic game, and his information about the game and links to other sources was very helpful.  But I didn't have to replicate this method.  I could just use the CLEAR command to define the end of memory that BASIC is allowed to use.

CLEAR500,26384

Then I just poked the dungeon into the space above 26384. This second argument of CLEAR is usually for defining an area to POKE any machine language subroutines that your BASIC program might call using the USR or EXEC functions.  But its also handy for simply protecting an area for poking data into.  I guess the PET doesn't have this function or the programmer simply used a different method.  I've certainly used blank strings, usually in the form of array strings, to define areas to POKE info into.  It's a very memory efficient method as long as the strings are not altered so they are switched around in string space.  I usually use the VARPTR function to find the beginning of the various indexed array strings, and then POKE using the address returned.  But I didn't use that method here as the program itself uses a method of a single continuous space in memory like the screen memory somehow defined by the string declaration of the early version of PET BASIC, but not in the second version.  Robin was able to patch this code so it worked on the more common updated version of BASIC.

Since the MC-10 screen is smaller than the PET's I also made the dungeon generating routine use all the space in the box defined by the impermeable outside wall around the dungeon. The rooms therefore can butt right up against the outer walls. I also decreased the max room size from 9 to 7.  Hopefully these changes maximize the space for the dungeon.  My efforts at such re-scaling were helped by the fact that the program uses variables to define the horizontal and vertical screen size of the dungeon/screen area.  It makes me wonder whether the dungeon engine had been designed for some generic BASIC system and then utilized by Sawyer.  Either that or he possibly planned to create versions of the program for other systems.

One final oddity. The following code from the monster movement routine has a number 31 in it:

910 IFA=41THENA=39
920 IFA=-39THENA=-41
930 GOTO960
940 IFA=31THENA=41
950 IFA=-41THENA=-39

When moving up or down in a 40 column screen numbers like 40,-40,39-39, 41 and -41 make sense. They allow movement in the up, down and horizontal directions. But 31 doesn't make sense except for a 32 column screen like the MC-10 has. For that kind of screen you want values like 32,-32,31,-31,33 and -33.  It might just be that someone inadvertently modified the original PET source, but it seems strange. I got my source from PYDungeon on Github, who has made a port of the game to the modern language Python. But it might be another indication that the game was originally designed for a different system from the PET with a different screen resolution. Perhaps the KIM?  Who knows.
 
My source can be found here:


How to play

PETDUNG can be played at my GameJolt site under the "More 8-bit BASIC game ports" menu item.


Just select Play Game, "More 8-bit BASIC game ports", and then select PETDUNG from the Cassette Menu, and type RUN and hit Enter in the Main emulator screen.

Wednesday 27 December 2023

The High Mountains by Paul Braithwaite (1984)

This is a unique multi-player text adventure game loosely based on John Christopher's Tripods trilogy. It allows players to take the roles of the human resistance or the alien masters and their tripods. Originally published as a type-in game for the ZX Spectrum in the British magazine Personal Computer News #79, my version is a port to the TRS-80 MC-10 using Micro Color BASIC from source for the Dick Smith VZ-200.

I remember there being lots of bugs in the code from the VZ. Some of these are outlined by Chickenman in his handy map and walkthrough which can be found on the Solution Archive.  He apparently ported the code from the original Sinclair version, so the bugs might be endemic rather than just in the VZ conversion that I worked from.

I'm posting about this game now despite the fact that I ported it many years ago because I recently revisited the code because Greg Dionne sent me a bunch of printouts from his BASIC compiler and his attempts to compile various of my programs. Most of these reports consisted of missing line numbers for GOTO and GOSUB statements (or THENs). Others regarded variables that are never declared or declared but never used.  Most of these latter problems are not catastrophic. They just represent some wasted memory. But sometimes a mistyped variable can affect the operation of the game. I don't think I have found any of that type yet in any of the games I've looked at but I'm working through the list to see if I can find any.  And I'm also getting ride of redundant variables in games that I know are near the max of memory so I can reduce any possibilities of Out-of-Memory (OM) errors.  

The latter was the case with "The High Mountains." I knew that this was a big program, so when Greg's compiler reported an unused Array, I went to weed it out. When I was looking at the code I realized that there were still many memory saving tricks that I hadn't applied. For example, replacing all ,0, references in DATA statements with ,, references since MS BASIC will just assume a 0 for such instances of double commas. I took the quote marks off all text DATA statement except for sentences with commas in them, since commas are used by DATA commands to separate items. I got rid of any <>0 references in IF statements, since all non-zero variable values are treated as true. I also updated my standard word-wrap routine with a shorter version that I had developed since making my port of MOUNTAIN.  

When I was finished I realized that I had freed up quite a bit of space. In fact I had enough space to add a title screen.  So I tried to recreate the Tripod rampaging image of the original Sinclair version (see the pic at the top of this post). I think it came out pretty well.

Another reason I am writing about this game is that in replaying it I remembered a few more bugs from my conversion process that were not mentioned in Chickenman's walkthrough. The biggest bug involved the command "RIDE" that one could use to travel on various objects in the game. Chickenman mentions fixing the BOAT routine to make it work properly, but he mentions "GET IN" rather than RIDE as the command for using it.  I remembered that I had fixed a number of transport items so their ride function worked. In addition to the BOAT there is a CAR and a HORSE and a TRAIN, all of which you can ride in a particular direction.  You just type RIDE TRAIN SOUTH or RIDE CAR WEST and you will go as far as possible in that direction until you hit a barrier to normal in game movement in that direction. You don't see any of the intervening spaces, so there might be advantages to avoiding use of this feature while exploring. But this feature is great for getting around fast in the game. The Masters and Tripods are not able to use this method, so perhaps in a real game the human characters were intended to use these objects to help them make quick getaways.  The map seems specifically designed to limit the pathways for these items to specific L and U-shaped circuits.

Another missing aspect from Chickman's walkthrough involved the final puzzle.  In my version of the game the player must use the BAG item, which can be found in Wichester village where the character Henry starts.  That item is needed to help with the transfer of the HYDROGEN to the BALLOON in the cave.  In my version there are 3 and 4 word commands for doing this like FILL BALLOON WITH HYDROGEN. I wonder if Chickenman took some of this complexity out, because he mentions a two step process of first issuing the command FILL BALLOON and then responding to a prompt for "WITH WHAT?"  I don't think I added these features and I'm pretty sure the bag is in there from the original.  

He also mentions another fix I that also found, which is that the random movement of NPCs could have them wander right off the map grid.  If you were playing the bad guys you might not actually be able to win because characters you need to kill would disappear forever.  He also mentions not having to engage in any combat. This is definitely a part of my port's operation, but I remember there being some weirdness with this routine as well and possibly I added some fixes to get combat to operate properly.  I can't remember exactly.  Maybe I'll get my son Charlie to exercise some Github skills to help me track back through the changes.

Anyway, I thought I should document some of these aspects of my porting recollections in case anyone is interested. It is a pretty unique game. I can't think of any other multiplayer text adventures from the early 8-bit era that I am aware of.  I'd love to actually see two players try to play this game against each other.  My son Charlie wasn't willing, and I knew the game too well from inside the code for any such match-up to have been fair.  Maybe some day someone, perhaps Renga in Blue (Jason Dyer) will do this.

While I'm documenting my recent programming efforts, I'll also note another text adventure that I fixed up in terms of memory use and title screen and obscure actions involving improper GOTO statement, references. The Treasure of Elgon Adventure is another neat text adventure.  It has a Grue in it, which if I recall correctly will disappear back into a wall if handled correctly.  Very Creepy.

And I made a few fixes to Jason "Night of the Vampire Bunnies" and Greg Hassett's "Sorcerer's Castle" and "Journey to the Center of the Earth." Some of these fixes involve very obscure in game commands, which would have errored under rare circumstances because of messed up GOTO references.  I also updated the standard word-wrap and reverse subroutines in these old ports and added new title screens:

Night of the Vampire Bunnies:


Journey to the Center of the Earth


The Sorcerer's Castle

Hassett's "Sorcerer's Castle"