Thursday 29 December 2022

"Dr. Who Adventure" by James Smith (1982)

I ported this text adventure quite some time ago, but my techniques for squeezing games into the 20K space of the MC-10 have improved a lot since then.  I now don't have to use the two-file data-loading methods that I discuss in that post.  I've learned other ways to save memory space, especially regarding the management of string space.  By renumbering lines by ones and using all my other memory saving techniques I have now got Dr. Who Adventure to fit into 20K.

I worked from a scan of this game first published in Australian magazine Micro-80, Volume 3, Issue 8.  It was not a very good scan, so it was a real challenge to get the game working.  And once I did I discovered a very challenging early 8-bit BASIC text adventure. Originally requiring the loading of two separate programs to allow it to fit in the memory of a 16K TRS-80 Model 1, I have finally succeeded in modifying it to work as a single program for the TRS-80 MC-10.  I have also made some bug fixes (many of which I can't remember). However, the most significant is probably this one:

890 IFRND(0)>.998ANDWTANDPS<>99PRINTSY"hit over the back of the head and everything goes black...You awake to find that everything you were holding is gone.":FORI=2TO16:IFO(I,1)=90THENO(I,1)=6:NEXTI:GOTO840ELSENEXTI:GOTO840

This routine involves you getting mugged and all your items NO(I,16) from I=2 to I=16 being moved to location 6. Unfortunately, Smith did not also add the code needed to deduct the "weight" of each item from your inventory. They just get re-located. Since you have a max weight of 20 (each item has its own distinct weight), once you are mugged it's possible that if you recover the items you won't be able to carry all the ones you need back to Galafry to win the game. You have to be carrying the items when you reach the throne room and "talk" with the other Timelord there. Other items also "disappear" without subtracting their weight, but most of these were game ending anyway, since they involve you giving away or eating items, etc. that you need to win. In any case, I rationalized all the dropping/giving /eating routines to subtract the weight of the lost items.

Another significant bug involves the jumping out of FOR/NEXT loops. This has the practical impact for memory saving that all NEXTs have to include the variable reference, otherwise strange results can occur in the return to the top of unclosed FOR loops. The offending code occurs in the very fancy multiple word parsing subroutine:
870 FORI=1TOJ:SW(I)=LEFT$(SW(I)+"   ",3):NEXTI:K=0:FORI=1TOJ:A1=1:AN=78:FORI1=1TO78:AI=INT((A1+AN)/2):X$=MID$(SC,AI*3-2,3):IFSW(I)>X$A1=AI+1ELSEAN=AI-1
I unraveled all the ELSEs used in this code and then made it so that the FOR/NEXT loops exit gracefully. This allowed me to remove all the variable references attached to NEXTs.  And it also prevents the variable stack from blowing its lid, which is deadly when you're trying to save every byte.

I have also changed some of the parameters of the game that were overly frustrating. You used to be limited to a random number of Tardis rides, which ranged from 20-40. Since the planets the Tardis goes to are arbitrary whenever you "reset" it, the game can be quite arbitrary in the level of challenge it presents.  I simply set it to 40. The random location selection is challenge enough.  I also changed the "search" function to a much lower level of possibility of not revealing items hidden in rooms.  As well, I made the "Renticulator" device report the exact number of required items that you have found.  It used to report a randomized "approximate" number. I made it report the exact number of required items  because it will be tough enough for people to figure out what it does, although a hint is given in the instructions published in the magazine and included in the CASA: Solutions archive description of the game.

Smith obviously loved using randomness to make his game more challenging, but it was to an extreme extent-- a typical flaw in early BASIC text adventure games.  Many authors of the era took grotesque pleasure in making their games diabolically tricky.  But it could often be too much.  In this game there are random mazes and random events a plenty, such as the "mugging" or walking off cliffs etc., so I don't feel bad about toning down the arbitrariness.  There is a really clever game here under all the gratuitous arbitrariness, with lots of interesting NPC interactions (for an 8-bit BASIC game) and a clever sense of humour, which I want other people to try and enjoy.

'PlayDalek' is pretty hot stuff

DRWHO can be played online here:

The VMC10 Emulator with DRWHO in the JIMG subdirectory of the Cassette directory can be downloaded here:

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