CONST FALSE      = 0
CONST TRUE       = NOT FALSE
CONST SHOWLORES  = $C056
CONST KEYBOARD   = $C000
CONST KEYSTROBE  = $C010
CONST EMPTY      = 0
CONST TREE       = 4
CONST FIRE       = 13
CONST FORESTSIZE = 42*42
BYTE  HELLOMSG[] = "PRESS ANY KEY TO BEGIN..."
BYTE  EXITMSG[]  = "PRESS ANY KEY TO EXIT."
BYTE  GOODBYE[]  = "THAT'S ALL FOLKS!"
BYTE  TREES1[FORESTSIZE]
BYTE  TREES2[FORESTSIZE]
WORD  RNDNUM
;
; Defines for ASM routines
;
ASM EQUATES
        SRC     EQU     $F0
        SRCL    EQU     SRC
        SRCH    EQU     SRC+1
        DST     EQU     SRC+2
        DSTL    EQU     DST
        DSTH    EQU     DST+1
        ESP     EQU     DST+2
END
;
; CALL 6502 ROUTINE
; ROMCALL(AREG, XREG, YREG, STATUS, ADDR)
;
ASM ROMCALL
TMP	EQU	$06

	PHP
	LDA	ESTKL,X
	STA	TMP
	LDA	ESTKH,X
	STA	TMP+1
	INX
	LDA	ESTKL,X
	PHA
	INX
	LDA	ESTKL,X
	TAY
	INX
	LDA	ESTKL+1,X
	PHA
	LDA	ESTKL,X
	INX
	STX	TMP+2
	TAX
	PLA
	BIT	ROMIN
	PLP
	JSR 	JMPTMP
	PHP
	BIT	LCBNK2
	STA	REGVALS+0
	STX	REGVALS+1
	STY	REGVALS+2
	PLA
	STA	REGVALS+3
	LDX	TMP+2
	LDA 	#<REGVALS
	LDY 	#>REGVALS
	STA 	ESTKL,X
	STY 	ESTKH,X
	PLP
	RTS
JMPTMP:	JMP	(TMP)
REGVALS: DS	4
END
;
; GRCOLOR(COLOR)
;
ASM GRCOLOR
	LDA	ESTKL,X
	INX
	STX	TMP+2
	BIT	$C081
	JSR 	$F864
	BIT	$C080
	LDX	TMP+2
END
;
; GRPLOT(X, Y)
;
ASM GRPLOT
    LDA	ESTKL,X
	INX
	LDY	ESTKL,X
	INX
	STX	TMP+2
	BIT	$C081
	JSR 	$F800
	BIT	$C080
	LDX	TMP+2
END
;
; SET MEMORY TO VALUE
; MEMSET(VALUE, ADDR, SIZE)
;
ASM MEMSET
        LDY     #$00
        LDA     ESTKL+1,X
        STA     DSTL
        LDA     ESTKH+1,X
        STA     DSTH
        INC     ESTKL,X
        INC     ESTKH,X
SETMEM: DEC     ESTKL,X
        BNE     :+
        DEC     ESTKH,X
        BEQ     MEMEXIT
:       LDA     ESTKL+2,X
        STA     (DST),Y
        INY
        BNE     :+
        INC     DSTH
:       DEC     ESTKL,X
        BNE     :+
        DEC     ESTKH,X
        BEQ     MEMEXIT
:       LDA     ESTKH+2,X
        STA     (DST),Y
        INY
        BNE     SETMEM
        INC     DSTH
        BNE     SETMEM
MEMEXIT: INX
        INX
        INX
END
;
; PRINT STRING
; PRSTR(STR)
;
ASM PRSTR
        LDY     #$00
        LDA     ESTKL,X
        STA     SRCL
        LDA     ESTKH,X
        STA     SRCH
        BIT     ROMIN
        LDA     (SRC),Y
        STA     ESTKL,X
        BEQ     :+
_PRS1:  INY
        LDA     (SRC),Y
        ORA     #$80
        JSR     $FDED
        TYA
        CMP     ESTKL,X
        BNE     _PRS1
:       INX
        BIT     LCBNK2
END
DEF TEXTMODE
  DROP ROMCALL(0, 0, 0, 0, $FB39)
END

DEF HOME
  DROP ROMCALL(0, 0, 0, 0, $FC58)
END

DEF GOTOXY(X, Y)
  ^($24) = X
  DROP ROMCALL(Y, 0, 0, 0, $FB5B)
END

DEF GRMODE
  DROP ROMCALL(0, 0, 0, 0, $FB40)
  DROP ^SHOWLORES
END

DEF RANDOMIZE(SEED)
  RNDNUM = (SEED << 8) ? (SEED >> 8 & $FF) + SEED
END

DEFOPT RND
  RNDNUM = (RNDNUM << 8) + RNDNUM + 12345
  RETURN RNDNUM & $7FFF
END

DEFOPT BYFIRE(TREEPTR)
  IF    ^(TREEPTR - 43) == FIRE
    RETURN TRUE
  ELSIF ^(TREEPTR - 42) == FIRE
    RETURN TRUE
  ELSIF ^(TREEPTR - 41) == FIRE
    RETURN TRUE
  ELSIF ^(TREEPTR - 1)  == FIRE
    RETURN TRUE
  ELSIF ^(TREEPTR + 1)  == FIRE
    RETURN TRUE
  ELSIF ^(TREEPTR + 41) == FIRE
    RETURN TRUE
  ELSIF ^(TREEPTR + 42) == FIRE
    RETURN TRUE
  ELSIF ^(TREEPTR + 43) == FIRE
    RETURN TRUE
  FIN
  RETURN FALSE
END
DEFOPT FORESTFIRE
  WORD NEWTREES, OLDTREES, NEWTREE, OLDTREE, YROW
  BYTE X, Y

  MEMSET(EMPTY, @TREES1, FORESTSIZE)
  MEMSET(EMPTY, @TREES2, FORESTSIZE)
  OLDTREES = @TREES1
  NEWTREES = @TREES2

  FOR Y = 1 TO 40
    YROW = Y * 42
    FOR X = 1 TO 40
      IF RND < 16384
        ^(OLDTREES + X + YROW) = TREE
      FIN
    NEXT
  NEXT
  WHILE ^$C000 < 128
    FOR Y = 1 TO 40
      YROW = Y * 42
      FOR X = 1 TO 40
        OLDTREE = OLDTREES + X + YROW
        NEWTREE = NEWTREES + X + YROW
        WHEN ^OLDTREE
          IS EMPTY
            IF RND < 400
              ^NEWTREE = TREE
            ELSE
              ^NEWTREE = EMPTY
            FIN
          IS TREE
            IF RND < 10 OR BYFIRE(OLDTREE)
              ^NEWTREE = FIRE
            ELSE
              ^NEWTREE = TREE
            FIN
          IS FIRE
            ^NEWTREE = EMPTY
        WEND
        GRCOLOR(^NEWTREE)
        GRPLOT(X - 1, Y - 1)
      NEXT
    NEXT
    NEWTREES =, OLDTREES = OLDTREES, NEWTREES
  LOOP
  DROP ^$C010
END

PRSTR(@HELLOMSG)
WHILE ^$C000 < 128
  RNDNUM = RNDNUM + 1
LOOP
RANDOMIZE(RNDNUM)
DROP ^$C010
GRMODE
HOME
GOTOXY(10,22)
PRSTR(@EXITMSG)
FORESTFIRE
TEXTMODE
HOME
PRSTR(@GOODBYE)
DONE