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game design.3
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2022-08-26
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╟AME ─ESIGN FOR THE ├-64
┬Y ╥OBERT ┴LONSO
<CONTINUED FROM PREVIOUS ARTICLE>
┴LIENS, ┴IRPLANES AND ╙YMBOLS
╬OW THAT YOU HAVE A COMPLETE CUSTOM
CHARACTER PROGRAM, YOU CAN START TO
DESIGN SOME ALIEN CREATURES,
AIRPLANES, OR ANY OTHER GRAPHIC SYMBOL
YOU MIGHT LIKE TO SEE IN YOUR
PROGRAMS. ╧NE VERY PRACTICAL
APPLICATION OF CUSTOM CHARACTERS IS
FOR FOREIGN ALPHABETS LIKE THE ╞RENCH
ALPHABET, WHICH USES ACCENT MARKS.
├USTOM CHARACTERS ARE GOOD TO HAVE,
BUT SINGLY THEY REALLY DON'T LOOK LIKE
MUCH ON THE SCREEN BECAUSE ├OMMODORE
64 CHARACTERS ARE VERY SMALL. ╘O
REALLY HAVE A DISTINGUISHABLE DESIGN,
YOU WILL HAVE TO CREATE SEVERAL
CHARACTERS AND PLACE THEM SIDE BY SIDE
OR ONE ON TOP OF THE OTHER. ╘O
ACCOMPLISH THIS, ALL THAT YOU WILL
HAVE TO DO IS DRAW TWO EIGHT-BY-EIGHT
GRIDS AND LAY THEM OUT SIDE BY SIDE ON
A FLAT SURFACE.
╬OW DESIGN YOUR CHARACTERS AND PLACE
BOTH SETS OF DATA STATEMENTS INTO
PROGRAM TWO. ┴LL YOU HAVE TO DO IS
PLACE THE SECOND SET OF DATA IN A NEW
PROGRAM LINE FOLLOWING LINE 90 AND
CHANGE THE ┘+7 OF LINE 70 TO ┘+15.
╘HE PROGRAM WILL NOW PUT THE FIRST
CHARACTER INTO THE LETTER THAT ┴$ IS
SET EQUAL TO AND THE SECOND CHARACTER
INTO THE LETTER FOLLOWING THAT ONE.
╞OR EXAMPLE, IF THE PROGRAM IS ONLY
MODIFIED IN LINE 70 AND THE EXTRA DATA
ADDED INTO A NEW LINE 95, YOU WOULD
END UP WITH THE FIRST CHARACTER DESIGN
WHERE THE LETTER ┴ USED TO BE AND THE
SECOND CHARACTER DESIGN WHERE THE
LETTER ┬ USED TO BE. ╔F YOU PRESSED
THE LETTERS ┴ AND ┬ ON THE KEYBOARD,
YOU WOULD THEN GET THE ORIGINAL
CHARACTER THAT YOU DESIGNED. ╘HIS
TECHNIQUE CAN BE EXPANDED TO INCLUDE
NUMEROUS CHARACTERS THAT YOU CAN
╨╥╔╬╘ SIDE BY SIDE AND ONE ON TOP OF
THE OTHER ON A SCREEN TO CREATE
COMPLEX GRAPHIC DISPLAYS.
═ULTI-├OLOR ├HARACTERS
├USTOM CHARACTERS CAN ALSO BE
CREATED IN MULTI-COLOR. ╘HIS MEANS
THAT YOU CAN TAKE A CHARACTER AND
INSTEAD OF JUST SEEING IT IN TWO
COLORS--THE CHARACTER'S COLOR AND THE
BACKGROUND COLOR--YOU CAN SEE IT IN
FOUR COLORS. ╘HESE COLORS ARE:
CHARACTER COLOR, BACKGROUND COLOR,
BACKGROUND COLOR 1, AND BACKGROUND
COLOR 2. ╘HESE COLORS ARE CONTROLLED
BY THE REGISTERS AT MEMORY LOCATIONS
53280, 53281, AND 53282. ╘HE
CHARACTER COLOR IS SET INDIVIDUALLY BY
POKING THE CORRECT VALUE INTO COLOR
╥┴═ AT 55296.
╘HE BINARY CODING NECESSARY FOR
CREATING MULTI-COLOR CHARACTERS
GENERALLY FOLLOWS THE SAME THEORY THAT
CREATING ONE-COLOR CUSTOM CHARACTERS
DOES, BUT THERE ARE SOME DIFFERENCES.
╔N A ONE-COLOR CUSTOM CHARACTER, EACH
BIT WHICH IS TURNED ON REPRESENTS THE
CHARACTER'S COLOR, BUT IN A MULTI-
COLOR CUSTOM CHARACTER EVERY TWO BITS
REPRESENT ONE OF THE FOUR POSSIBLE
COLORS. ┬ECAUSE OF THIS, SOME
HORIZONTAL RESOLUTION IS LOST. ╙INCE
EACH HORIZONTAL ROW HAS EIGHT BITS,
THAT MEANS THAT THERE ARE ACTUALLY
FOUR TWO-BIT PIXELS, (OR NYBBLES, AS
THEY ARE OFFICIALLY CALLED). ╔F BOTH
BITS OF A NYBBLE ARE TURNED ON, THEN
THAT NYBBLE BECOMES THE COLOR
SPECIFIED BY COLOR ╥┴═. ╔F BOTH ARE
OFF, THEN THAT NYBBLE IS COLORED WITH
THE BACKGROUND COLOR SPECIFIED BY
MEMORY LOCATION 53281. ╘HE OTHER TWO
COLORS ARE PRODUCED BY A ONE-BIT-ON,
ONE-BIT-OFF COMBINATION. ╘HE
FOLLOWING CHARTS MAY BE HELPFUL TO
YOU.
╘┴┬╠┼ 1
00 ┬ACKGROUND COLOR -╨╧╦┼ 53281,COLOR
01 ┬ACKGROUND 1 -╨╧╦┼ 53282,COLOR
10 ┬ACKGROUND 2 -╨╧╦┼ 53283,COLOR
11 ├OLOR IN ╥┴═
╘┴┬╠┼ 2
0 00 00 00 00 -BACKGROUND COLOR
85 01 01 01 01 -COLOR AT 53282
170 10 10 10 10 -COLOR AT 53283
255 11 11 11 11 -COLOR ╥┴═
0 00 00 00 00
85 01 01 01 01
170 10 10 10 10
255 11 11 11 11
╘HE NUMBERS IN ╘┴┬╠┼ 2 WILL PRODUCE
A STRIPED CUSTOM CHARACTER IF THEY ARE
╨╧╦┼D INTO MEMORY USING THE SECOND
EXAMPLE PROGRAM. ╘O SEE IT IN MULTI-
COLOR MODE, THOUGH, YOU WILL HAVE TO
USE THE FOLLOWING LINE TO ENABLE
MULTI-COLORED CHARACTERS:
╨╧╦┼ 53270,╨┼┼╦(53270) ╧╥ 16
┴FTER YOU ARE DONE WITH THE
DEMONSTRATION, YOU CAN DISABLE THE
MULTI-COLOR MODE BY TYPING IN THE
FOLLOWING LINE:
╨╧╦┼ 53270, ╨┼┼╦(53270) ┴╬─ 239
╘HE NEXT EXAMPLE PROGRAM USES A
DIFFERENT TECHNIQUE FOR LOADING DATA
INTO THE CORRECT ╥┴═ LOCATIONS. ╘HE
DIFFERENCE IS IN HOW IT OBTAINS ITS
VALUE FOR ┴$. ╔NSTEAD OF HAVING ┴$
ASSIGNED A VALUE AT THE BEGINNING OF
THE PROGRAM, THE VALUE IS OBTAINED
FROM THE DATA STATEMENTS. ╔F YOU WERE
TO HAVE MANY CHARACTERS THAT YOU
NEEDED CUSTOMIZED, YOU COULD USE THIS
TECHNIQUE EASILY. ╩UST MAKE THE
SECOND NUMBER OF THE LOOP (╪1) AT LINE
40 THE NUMBER OF CHARACTERS YOU ARE
REDEFINING (CURRENTLY IT IS A 2). ╘HE
FIRST CHARACTER IN EACH DATA STATEMENT
SHOULD BE THE LETTER THAT YOU WANT
REDEFINED.
╘HE THIRD EXAMPLE PROGRAM WILL
PRINT A SMALL SPACESHIP IN THE UPPER-
LEFT CORNER OF THE SCREEN. ╘HE
SPACESHIP IS COMPOSED OF WHAT USED TO
BE LETTERS ┴ AND ┬ SIDE BY SIDE, THUS
ILLUSTRATING THAT A CUSTOM CHARACTER
CAN BE MORE THAN ONE CHARACTER WIDE.
╘HE SPACESHIP IS IN MULTI-COLOR AND SO
IS THE REST OF THE SCREEN. ┬ECAUSE
OF THIS, YOU MAY HAVE A VERY DIFFICULT
TIME TRYING TO PLAY AROUND WITH SOME
DIFFERENT ╨╧╦┼S BECAUSE YOU MIGHT NOT
BE ABLE TO READ YOUR SCREEN VERY WELL.
╘HE STRIPES THAT COMPOSE THE SPACESHIP
WILL CHANGE COLORS AS YOU ╨╧╦┼ NEW
VALUES INTO THESE LOCATIONS.
------------
╔N FUTURE COLUMNS, YOU WILL FIND OUT
WHAT A SPRITE IS AND HOW TO CREATE
ONE. ┘OU WILL ALSO LEARN HOW TO
DETECT COLLISIONS BETWEEN SPRITES AND
COLLISIONS BETWEEN SPRITES AND YOUR
BACKGROUND.
╘HE NEXT INSTALLMENT OF THIS COLUMN
WILL BE DEVOTED TO PROGRAMMING CUSTOM
CHARACTERS IN MACHINE LANGUAGE.
╔F YOU WOULD LIKE TO ╥╒╬ THE THIRD
AND LAST EXAMPLE PROGRAM FOR THIS
MONTH, PRESS THE '\' KEY NOW. ┬ECAUSE
\OAD"GAME PROG-3",8
OF THE NATURE OF THIS PROGRAM, IT DOES
╬╧╘ RETURN TO ╠╧┴─╙╘┴╥. ┴FTER RUNNING
THIS PROGRAM, PLEASE TURN YOUR
COMPUTER OFF BEFORE RE-ENTERING
╠╧┴─╙╘┴╥.
----------< END OF ARTICLE >----------