Precision Software Appli…tions Silver Collection 1/Precision Software Applications Silver Collection Volume One (PSM) (1993).iso/tutor/advtutr.exe/ADVENT6.DOC

Text File | 1986-08-31 | 7KB | 170 lines

                      How to Write an Adventure
                           Part 6

Advanced techniques and routines

     While the adventure, as outlined in the previous files WILL run, there
are alot of elegant touches we can give the game to make it look and behave
more professionally. Those ideas to be covered in this files are:
     1. Display Inventory
     2. Command Shorthand
     3. Display a Word List
     4. Opening invisable doors
     5. Saves and Loads
     6. Ending the game
     7. Machine specific ideas for better appearance

INVENTORY

     Since your puppet in the adventure can pick up and put dowm things, it
would be nice to have some sort of routine to display what it is that he is
holding at any given time. This is done by making just a few changes to the
VISABLE OBJECTS routine in the display screen and placing it in a routine to
be accessed by the one word command "INVENTORY". Here's the code:

     13000 Z=0:PRINT"YOU ARE CURRENTLY HOLDING: ";
     13010 FOR X=1 TO OBJECTS:IF L(X)<>-1 THEN 13050
     13020 IF Z<>0 THEN PRINT", ";
     13030 IF POS(0)+LEN(OBJECT$(X))+3>79 THEN PRINT
     13040 PRINT OBJECT$(X);
     13050 NEXT:IF Z=0 THEN PRINT "NOTHING":GOTO 1000
     13060 PRINT:GOTO 1000

     As you can see this routine is identical to the earlier routine EXCEPT
that instead of testing for an object being located in room L, we test for it
being located in room -1 (the puppet's hands).

SHORTHAND

     We have been assuming all long that the command parser is working with
the full words that you have chosen for communications. To quote an old song
"It tain't necessarily so!". You can save memory, and make the typing chores
of your players lighter by making the parser interpret only the first 3 or 4
letters of the word (whichever is enough to remove ambiguity). Here's how we
do that.
     When the parser breaks the input string down into VERB$ and NOUN$, add to
the code a line that does the following:

     10?? VB$=LEFT$(VERB$,3):NN$=LEFT$(NOUN$,3)

     Now, instead of using NOUN$ and VERB$ in the compare loops of the parser,
use VB$ and NN$. You likewise should adjust your verb and noun lists to
contain the shortened words instead of the whole words as you indicated
earlier.
     This technique is by no means necessary, it's just nice to know about if
you get into a situation (as adventure authors always do) where they are
coming down to the wire and running out of memory faster than plot ideas!
     Another shorthand is the time-honored method of allowing the user to
input N for GO NORTH or U for GO UP. This again is east to code. Just add the
following lines IMMEDIATELY after the INPUT line of the parser input routine:

     1101 IF AN$="N" THEN AN$="GO NORTH"
     1102 IF AN$="E" THEN AN$="GO EAST"
     1103 IF AN$="S" THEN AN$="GO SOUTH"
     1104 IF AN$="W" THEN AN$="GO WEST"
     1105 IF AN$="U" THEN AN$="GO UP"
     1106 IF AN$="D" THEN AN$="GO DOWN"

     And last but not least, ANY one word command can be shortened to 3 or 4
character input by this coding technique:

     2000 IF LEFT$(AN$,3)="INV" THEN 13000
     2010 IF LEFT$(AN$,3)="HEL" THEN 11000

     and so on.

WORD LISTS

     This is a nice touch if you have the memory and the inclination.
Sometimes it is especially hard for a new adventurer to get the hang of just
how to phrase what he wishes to say. A "Words" list willdisplay all of the
words that the computer understands. It is just a print routine that has all
the full-length words typed into it and displayed when the one-word command
"WORDS" is issued.

OPENING INVISABLE DOORS

     The day will come when you want a door to open when something or the
other is done (like waving a wand or using a key). This is done by
manipulation of the D(X,6) array. When the triggering even occurs, let us say
you wish to open a door to the west. Do the following:

     23650 D(L,4)=16:GOTO 1000

     This opens a door from the current room to room 16. (The previous number
stored in D(L,4) was a 0).

SAVES and LOADS

     This also is a nice, much appreciated touch you can give your players.
This saves the current game situation to disk, so you can come back to that
point if you are killed, or if you get called to supper and have to shut the
machine off. It simply consists of a routine to save all the variables that
might be changed, and call them back later.
     Start by opening the save file, using whatever format your BASIC demands.
Next, save the locations of all objects:

     50010 FOR X=1 TO OBJECTS:PRINT #1, OBJECT$(X):NEXT

     Next, if the door configuration ever changes in your adventure (if you
allow doors to open or close), save your D array. This is NOT required if you
never modify this array.

     50020 FOR X=1 TO NUMBEROFROOMS:FOR Y=1 TO 6
     50030 PRINT #1,D(X,Y):NEXT Y:NEXT X

     Finally, save any flag variables you may have, and the current room
number L:

     50040 PRINT #1,L,QQ,KILLFLAG,PRIZEFLAG

     and then close your file. You will want to display an appropriate message
while this is going on.
     To restore the game, direct the program to code that will read all this
stuff back into the arrays, in the same order.


ENDING THE GAME

     By the way, Hemmingway, please be sure to include some sort of a printed
statement in the adventure to the effect that the whole puzzle has been
solved, and the adventure is over. I remeber playing one for two days after
I'd solved it all because it didn't bother to TELL ME THAT!


MACHINE SPECIFIC STUFF

     I have made a very genuine attempt so far to do all coding in PLAIN
VANILLA BASIC... BASIC that will run on any computer. This code, however,
produces an adventure whose status screen scrolls off the screen, and is
replaced after each event. A more attractive coding is possible, but it
requires more sophistocated coding, and is different for each machine we
support here. I'm going to discuss what happens here, and then direct you to
another file in the library that has the revised parser for your particular
machine.

     The simplist way to keep the display screen at the top of the screen is
to clear it after each action. This is not cool, though, because the adventure
plays easier if the player can see his last few moves still displayed in a
screen scroll. This can be done on all machines, but requires manipulation of
the cursor on the screen, and some additional code to clean up potential
messes. Here is the sequence of events. Read and understand it, then look at
the file for your machine and try to understand how the code does these
things.
     1. Position the cursor at the upper left-hand corner of the screen.
     2. Reprint the status screen (updated), but be sure the erase anything to
the right of the last thing written on each line. This is required to cover up
garbage that collects from the bottom of the screen.
     3. Blank the line just below the line of dashes.
     4. Position the cursor on the left-hand side of the bottom line of the
screen.
     The examples are saved as:
     IBM.SCR
     APPLE.SCR
     COMM.SCR