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| assume cs:code, ds:data, ss:stack
; gpu prop byte
; 7 6 5 4 3 2 1 0
; BL R G B I R G B
; | \_____/ | \_____/
; 闪烁 背景 高亮 前景
; game map: 25 x 25
; snake bodys max: 23 x 23
data segment
score dw 0 ; game score
scpre db 'score:' ; [6] score prefix
dead db 'game over!' ; [10] game over
food dw 0 ; snake food: x|y
sdct db 0 ; snake direction 0001-up 0010-down 0100-left 1000-right
slen db 0 ; snake length
body dw 529 dup(0) ; snake bodys: x|y, ...
data ends
stack segment
dw 20 dup(0)
stack ends
code segment
start:
mov ax, data
mov ds, ax ; init data seg
mov ax, 0b800h
mov es, ax ; save gpu base addr
mov ax, stack
mov ss, ax
mov sp, 20 ; init stack
call clear
mov ah, 24
mov al, 24
push ax
call draw_map
call create_snake
call draw_snake
call create_food
call draw_food
call start_game
call show_score
end_game:
call game_over
mov ax, 4c00h
int 21h
; # start game
; void -> void
start_game:
mov cx, 50
sg0:
call listen_key
call clear_last
call move_snake
call is_dead
call draw_snake
call is_eat
call show_score
call sleep
loop sg0
ret
; # show game over alert
; void -> void
game_over:
push ax
push cx
push si
mov si, 28
mov cx, 10 ; string length
go0:
mov ax, si
mov ah, al
mov al, 12
push ax
mov ah, 00000111b
mov al, dead[si - 28]
push ax
call draw_char
inc si
loop go0
pop si
pop cx
pop ax
ret
; # is the snake dead
; void -> void
is_dead:
push ax
push cx
push si
mov ax, body[0] ; get head
cmp ah, 0 ; touch the edge
je end_game
cmp ah, 24
je end_game
cmp al, 0
je end_game
cmp al, 24
je end_game
mov ch, 0
mov cl, slen
dec cx
mov si, 2 ; start with second
id0: ; touch self body
mov ax, body[si]
cmp body[0], ax
je end_game
add si, 2
loop id0
pop si
pop cx
pop ax
ret
; # add snake body
; void -> void
add_body:
push ax
push si
mov ah, 0
mov al, slen
inc al
mov slen, al ; add body
mov si, ax
add si, si
mov ax, body[si - 4]
mov body[si - 2], ax
inc score
call create_food
call draw_food
pop si
pop ax
ret
; # is snake eat food
; void -> void
is_eat:
push ax
mov ax, food
cmp ax, body[0]
jne nt0
call add_body
nt0:
pop ax
ret
; show game score
; void -> void
show_score:
push ax
push bx
push si
mov si, 28
mov cx, 6 ; string length
po0: ; draw score prefix
mov ax, si
mov ah, al
mov al, 2
push ax
mov ah, 00000111b
mov al, scpre[si - 28]
push ax
call draw_char
inc si
loop po0
mov si, 0
mov ax, score
sl0:
mov bh, 0
mov bl, 10
div bl
mov bx, ax
mov bl, bh
mov bh, 0
push bx ; save digit
inc si ; count digits
cmp al, 0 ; no more digit
je se0
mov ah, 0 ; next digit
jmp short sl0
se0:
mov cx, si
mov si, 34 ; show start x
sn0:
pop bx ; get each digit
add bx, 30H ; get digit ascii
mov ax, si
mov ah, al
mov al, 2
push ax
mov ah, 00000111b
mov al, bl
push ax
call draw_char ; draw each digit
inc si
loop sn0
pop si
pop bx
pop ax
ret
; # listen to keys
; void -> void
listen_key:
push ax
mov ah, 1
mov al, 0
int 16h ; keboard interrupt
cmp ah, 1
je lk0
mov ax, 0
int 16h
cmp ax, 4800h ; press up
je kup
cmp ax, 5000h ; press down
je kdown
cmp ax, 4b00h ; press left
je kleft
cmp ax, 4d00h ; press right
je kright
jmp short lk0
kup:
cmp sdct, 0010b ; direction conflict
je lk0
mov sdct, 0001b ; set direction
jmp short lk0
kdown:
cmp sdct, 0001b
je lk0
mov sdct, 0010b
jmp short lk0
kleft:
cmp sdct, 1000b
je lk0
mov sdct, 0100b
jmp short lk0
kright:
cmp sdct, 0100b
je lk0
mov sdct, 1000b
lk0:
pop ax
ret
; # clear last snake body
; void -> void
clear_last:
push ax
push si
mov ah, 0
mov al, slen
mov si, ax
add si, si
mov ax, body[si - 2] ; last body
push ax
mov ah, 00000000b
mov al, ' '
push ax
call draw_char ; clear
pop si
pop ax
ret
; # update snake bodys
; void -> void
move_snake:
push ax
push cx
push si
mov ch, 0
mov cl, slen
dec cx
mov ah, 0
mov al, slen
mov si, ax
add si, si
ms0:
mov ax, body[si - 4]
mov body[si - 2], ax
sub si, 2
loop ms0
mov ax, body[0] ; upd head
cmp sdct, 0001b ; up
je up
cmp sdct, 0010b ; down
je down
cmp sdct, 0100b ; left
je left
cmp sdct, 1000b ; right
je right
up:
dec al
jmp short uok
down:
inc al
jmp short uok
left:
dec ah
jmp short uok
right:
inc ah
jmp short uok
uok:
mov body[0], ax
pop si
pop cx
pop ax
ret
; # draw snake to map
; void -> void
draw_snake:
push cx
push si
push ax
mov ch, 0
mov cl, slen
mov si, 0
ds0:
mov ax, body[si]
push ax
mov ah, 01110000b
mov al, ' '
push ax
call draw_char ; draw body
add si, 2
loop ds0
pop ax
pop si
pop cx
ret
; # create snake
; fixed: snake size is 3
; void -> void
create_snake:
push cx
push si
push ax
mov sdct, 1000b ; set direct is right
mov ah, 1
mov al, 1
mov slen, 2 ; set snake length
mov ch, 0
mov cl, slen
mov si, 0
mov ah, 6 ; set snake head x
mov al, 4 ; set snake head y
c0:
mov body[si], ax
dec ah
add si, 2
loop c0
pop ax
pop si
pop cx
ret
; draw food to map
; void -> void
draw_food:
push ax
mov ax, food
push ax
mov ah, 00101000b
mov al, ' '
push ax
call draw_char ; draw food
pop ax
ret
; # create a food
; fixed: map width and height
; void -> void
create_food:
push ax
push bx
push cx
push dx
push si
re0:
mov bx, 23
push bx
call rand ; get x
inc dx ; range: 1-[23]
mov ah, dl
push bx
call rand ; get y
inc dx
mov al, dl
mov ch, 0
mov cl, slen
mov si, 0
sb0: ; for snake body
cmp ax, body[si]
je re0 ; conflict with body, create again
add si, 2
loop sb0
mov food, ax ; save food xy
pop si
pop dx
pop cx
pop bx
pop ax
ret
; # rand number
; 0: range -> dx: 0~(range)
rand:
push bp
mov bp, sp
push ax
mov ax, 0h
out 43h, al
in al, 40h
in al, 40h
in al, 40h
mov bx, [bp + 4]
div bl
mov dh, 0
mov dl, ah
pop ax
pop bp
ret 2
; # sleep tiem
; void -> void
sleep:
push cx
mov cx, 50000
s0:
push cx
mov cx, 20
s1:
loop s1
pop cx
loop s0
pop cx
ret
; # draw game map
; 0: width|height -> void
draw_map:
push bp
mov bp, sp
; draw top
push cx
push ax
push bx
push dx
mov dx, [bp + 4] ; get width
mov ax, 0
mov ch, 0
mov cl, dh ; set width
inc cl
d0:
mov bh, al ; draw top
mov bl, 0
push bx
mov bh, 00010000b
mov bl, ' '
push bx
call draw_char
mov bh, al ; draw bottom
mov bl, dl
push bx
mov bh, 00010000b
mov bl, ' '
push bx
call draw_char
inc al
loop d0
mov cl, dl ; set height
dec cl ; inside content height
mov al, 1
d1:
mov bh, 0 ; draw left
mov bl, al
push bx
mov bh, 00010000b
mov bl, ' '
push bx
call draw_char
mov bh, dh ; draw bottom
mov bl, al
push bx
mov bh, 00010000b
mov bl, ' '
push bx
call draw_char
inc al
loop d1
pop dx
pop bx
pop ax
pop cx
pop bp
ret 2
; # draw char to screen
; 0: x|y, 1: prop|char -> void
draw_char:
push bp
mov bp, sp
push ax
push bx
push si
mov bx, [bp + 6]
mov ah, 0
mov al, 0a0h
mul bl ; set y
mov bl, bh
mov bh, 0
add bl, bl
add bl, bl
add ax, bx ; set x
mov si, ax
mov ax, [bp + 4]
mov es:[si], ax ; set prop and char
cmp al, ' '
jne jm0
mov es:[si + 2], ax ; for edge, double draw.
jm0: ; for normal char
pop si
pop bx
pop ax
pop bp
ret 4
; # clear screen
; void -> void
clear:
mov ax, 3h
int 10h
ret
code ends
end start
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