In our PROC_executeCommand() procedure, you will find some code similar to the following:
WHEN com$ = "n" OR com$ = "north"
IF y%<3 THEN
y% += 1
ELSE
PRINT gridError$
ENDIF
Which, roughly translated means:
WHEN THE PLAYER WANTS TO MOVE NORTH
IF THE PLAYER IS NOT AT THE EDGE OF THE MAP
MOVE NORTH
ELSE
DISPLAY AN ERROR MESSAGE
A similar construction occurs at all of the compass directions.
 |
| A simple fix to check for walking off the edge of the map. In fact, you could allow the player to move off, but wrap around so that they appear on the other side of the map instead. |
Next time - adding objects.
Source code follows:
REM an adventure game in BB4W
REM by Mr Street
REM version 1.0.0.1 setting up the world
REM version 1.0.0.2 moving around the world
REM version 1.0.0.3 fixing it so you can't walk out of the grid
REM let's set up a 'world'
DIM World$(3,3) : REM creates a 3x3 grid
REM now 'populate' the grid with some space names
PROC_populateWorld
REM now some data about our player
REM player's starting position
x% = 2
y% = 2
REM player's health
health% = 50
PROC_main
DEFPROC_main
LOCAL command$ : REM user's input
REM the main program
REM repeat until the player is dead
REPEAT
REM show the player's current position
PROC_showCurrent
REM get some input from the player
INPUT "What now? > " command$
REM deal with user's input
PROC_executeCommand( command$ )
UNTIL health% <= 0
ENDPROC
DEFPROC_executeCommand( command$ )
REM deals with the users input
LOCAL com$, gridError$
gridError$ = "You can't go in that direction!" : REM a message for when you move off the grid
com$ = FN_convlc( command$ ) : REM convert to lowercase so it is easier
CASE TRUE OF
WHEN com$ = "n" OR com$ = "north"
IF y%<3 THEN
y% += 1
ELSE
PRINT gridError$
ENDIF
WHEN com$ = "s" OR com$ = "south"
IF y% >1 THEN
y% -= 1
ELSE
PRINT gridError$
ENDIF
WHEN com$ = "e" OR com$ = "east"
IF x%<3 THEN
x% += 1
ELSE
PRINT gridError$
ENDIF
WHEN com$ = "w" OR com$ = "west"
IF x%>1 THEN
x% -= 1
ELSE
PRINT gridError$
ENDIF
ENDCASE
ENDPROC
DEFPROC_showCurrent
PRINT "You are at the : "World$(x%, y%)
PRINT "Your health is : "STR$(health%)
ENDPROC
DEF FN_convlc(A$)
REM converts to lower case
SYS "CharLowerBuff", !^A$, LEN(A$)
= A$
DEFPROC_populateWorld
REM puts some names of the spaces into the World
LOCAL x%, y%
REM start with the first row
FOR y% = 1 TO 3
FOR x% = 1 TO 3
READ World$(x%,y%)
NEXT
NEXT
ENDPROC
:
REM the data for our 3x3 grid
DATA "Hills", "Mountains", "Forest"
DATA "Castle", "Village", "Fields"
DATA "Woods", "Swamp", "Lake"
In fact, a slightly improved program would have a constant variable that sets the size of the game world, allowing the programmer to change the size of the game world to any size they desire without breaking this bit. For the purpose of these posts we shall keep the size of the world fixed at '3', however I might be tempted to code like this instead:
REM an adventure game in BB4W
REM by Mr Street
REM version 1.0.0.1 setting up the world
REM version 1.0.0.2 moving around the world
REM version 1.0.0.3 fixing it so you can't walk out of the grid
REM - alternative version -
REM let's set up a 'world'
SIZE% = 3 : rem <--- sets the size of the world
DIM World$( SIZE%, SIZE% ) : REM creates a 3x3 grid
REM now 'populate' the grid with some space names
PROC_populateWorld
REM now some data about our player
REM player's starting position
x% = 2
y% = 2
REM player's health
health% = 50
PROC_main
DEFPROC_main
LOCAL command$ : REM user's input
REM the main program
REM repeat until the player is dead
REPEAT
REM show the player's current position
PROC_showCurrent
REM get some input from the player
INPUT "What now? > " command$
REM deal with user's input
PROC_executeCommand( command$ )
UNTIL health% <= 0
ENDPROC
DEFPROC_executeCommand( command$ )
REM deals with the users input
LOCAL com$, gridError$
gridError$ = "You can't go in that direction!" : REM a message for when you move off the grid
com$ = FN_convlc( command$ ) : REM convert to lowercase so it is easier
CASE TRUE OF
WHEN com$ = "n" OR com$ = "north"
IF y%<SIZE% THEN
y% += 1
ELSE
PRINT gridError$
ENDIF
WHEN com$ = "s" OR com$ = "south"
IF y% >1 THEN
y% -= 1
ELSE
PRINT gridError$
ENDIF
WHEN com$ = "e" OR com$ = "east"
IF x%<SIZE% THEN
x% += 1
ELSE
PRINT gridError$
ENDIF
WHEN com$ = "w" OR com$ = "west"
IF x%>1 THEN
x% -= 1
ELSE
PRINT gridError$
ENDIF
ENDCASE
ENDPROC
DEFPROC_showCurrent
PRINT "You are at the : "World$(x%, y%)
PRINT "Your health is : "STR$(health%)
ENDPROC
DEF FN_convlc(A$)
REM converts to lower case
SYS "CharLowerBuff", !^A$, LEN(A$)
= A$
DEFPROC_populateWorld
REM puts some names of the spaces into the World
LOCAL x%, y%
REM start with the first row
FOR y% = 1 TO SIZE%
FOR x% = 1 TO SIZE%
READ World$(x%,y%)
NEXT
NEXT
ENDPROC
:
REM the data for our 3x3 grid
DATA "Hills", "Mountains", "Forest"
DATA "Castle", "Village", "Fields"
DATA "Woods", "Swamp", "Lake"