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worm4.asm
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worm4.asm
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;*****************************************************
; WORM4
; Add in border around the screen
;*****************************************************
*=$1000
Const_KBD_BUFFER = $c5 ; Keyboard matrix
Const_UP = $09 ;
Const_DOWN = $0c ;values
Const_LEFT = $0a ;for up down left right
Const_RIGHT = $0d ;
Const_WORM_INCR = $16 ; "T" pressed = increase length of worm
;*****************************************************
; Initialize worm memory areas
;*****************************************************
ldx #00
lda #00
@init_loop lda headx
sta worm1x,x
lda heady
sta worm1y,x
dex
bne @init_loop
lda headx
sta worm1x
sta bodyx
lda heady
sta worm1y
sta bodyy
lda #$93 ; Clear the screen
jsr $ffd2
jsr draw_border
main_loop
lda offset
tax
lda worm1x,x
sta tempx
lda worm1y,x
sta tempy
clc
lda offset
adc length
tax
lda worm1x,x
sta bodyx
lda worm1y,x
sta bodyy
lda #$20 ; Erase starting position
pokeaxy tempx,tempy
jsr set_direction ; Change position of head
lda length
beq @no_body
lda #31 ; Draw body
pokeaxy bodyx,bodyy
@no_body inc offset
lda headx
clc
lda offset
adc length
tax
lda headx
sta worm1x,x
lda heady
sta worm1y,x
peekaxy headx,heady ; Hit detection
cmp #$20
@self bne @self
lda #$32 ; Draw head
pokeaxy headx,heady
;*****************************************************
; finish loop
;*****************************************************
jsr get_key
jsr delay
jmp main_loop
rts
;*****************************************************
; set_direction
;*****************************************************
set_direction
lda startdir
cmp #1
beq @down
cmp #2
beq @left
cmp #3
beq @right
@up dec heady
jmp @cont
@down inc heady
jmp @cont
@left dec headx
jmp @cont
@right inc headx
@cont
rts
;*****************************************************
; get input
;*****************************************************
get_key lda Const_KBD_BUFFER ; Input a key from Keyboard
_ck_pressed
cmp #Const_DOWN ; down - z pressed
beq @down
cmp #Const_Right ; up - w pressed
beq @right
cmp #Const_LEFT ; left - a pressed
beq @left
cmp #Const_Up ; right - s pressed
beq @up
cmp #Const_WORM_INCR ;T - Pressed - advance a level - cheat
beq @make_bigger
rts
@down
lda #1
sta startdir ; Down
rts
@right
lda #3
sta startdir ; Right
rts
@up
lda #0
sta startdir ; Up
rts
@left
lda #2
sta startdir ; left
rts
@make_bigger
inc length
lda length
clc
adc offset
tax
lda headx
sta worm1x,x
lda heady
sta worm1y,x
rts
;***DELAY ***
delay txa
pha
ldx #$20
@loop1 ldy #0
@loop2 dey
bne @loop2
dex
bne @loop1
pla
rts
height byte 25
width byte 40
Const_BOX_X byte 0
Const_Box_Y byte 0
Const_Box_Color byte 2
draw_border
lda #0
sta Const_Box_X
sta Const_Box_Y
lda #40
sta width
lda #25
sta height
ldy Const_BOX_Y
lda map_off_l,y
sta @left_top_edge+1
sta @left_top_edgec+1
lda map_off_h,y
sta @left_top_edge+2
lda Const_Screen_C,y
sta @left_top_edgec+2
clc
dey
tya
adc height
tay
lda map_off_l,y
sta @left_bot_edge+1
sta @left_bot_edgec+1
lda map_off_h,y
sta @left_bot_edge+2
lda Const_Screen_C,y
sta @left_bot_edgec+2
ldx Const_BOX_X
ldy #0
lda #$2
@left_top_edge sta $400,x
@left_bot_edge sta $450,x
lda Const_Box_Color
@left_top_edgec sta $d800,x
@left_bot_edgec sta $d800,x
inx
iny
@box_width cpy width
bne @left_top_edge-2
ldx #2 ; Accounts for top and bottom of box => just draw middle
ldy Const_BOX_Y
iny
@loop2 lda map_off_l,y
sta @box_top_left+1
sta @box_top_right+1
sta @box_top_leftc+1
sta @box_top_rightc+1
lda map_off_h,y
sta @box_top_left+2
sta @box_top_right+2
lda Const_Screen_C,y
sta @box_top_leftc+2
sta @box_top_rightc+2
txa
pha
ldx Const_Box_X
lda #$1
@box_top_left sta $400,x
lda Const_Box_Color
@box_top_leftc sta $d800,x
dex
txa
clc
adc width
tax
lda #1
@box_top_right sta $400,x
lda Const_Box_Color
@box_top_rightc sta $d800,x
pla
tax
inx
iny
cpx height
bne @loop2
rts
tempx byte 00
tempy byte 00
bodyx byte 00
bodyy byte 00
headx byte 06
heady byte 10
startdir byte 01,00
offset byte 00,00
length byte 00,00
map_off_l byte $00,$28,$50,$78,$A0,$C8,$F0,$18,$40,$68,$90,$b8,$E0,$08,$30,$58,$80,$a8,$d0,$f8,$20,$48,$70,$98,$c0
map_off_h byte $04,$04,$04,$04,$04,$04,$04,$05,$05,$05,$05,$05,$05,$06,$06,$06,$06,$06,$06,$06,$07,$07,$07,$07,$07
Const_Screen_C byte $d8,$d8,$d8,$d8,$d8,$d8,$d8,$d9,$d9,$d9,$d9,$d9,$d9,$da,$da,$da,$da,$da,$da,$da,$db,$db,$db,$db,$db
;*****************************************************
; Grab value of screen position located at x,y
; Store result in accumulator
;*****************************************************
defm peekaxy
ldx /2 ; X value
ldy /1 ; Y Value
lda map_off_l,x ; Load map low byte into $fb
sta $fb
lda map_off_h,x ; Load map hig byte into $fc
sta $fc
lda ($fb),y ; Load result into acc
endm
;*****************************************************
; Store value of accumulator in screen memory at position
; x, y
;*****************************************************
defm pokeaxy
pha
ldx /2 ; X value
ldy /1 ; Y value
lda map_off_l,x ; Load map low byte into $fb
sta $fb
lda map_off_h,x ; Load map high byte into $fc
sta $fc
pla
sta ($fb),y ; Store result in screen memory
endm
*=$2000
worm1x
*=$2100
worm1y