Ensamblador - Juego de Snake en Emu8086

name "snake"

org     100h

; jump over data section:

jmp     start

; ------ data section ------

s_size  equ     7

; the snake coordinates

; (from head to tail)

; low byte is left, high byte

; is top - [top, left]

snake dw s_size dup(0)

tail    dw      ?

; ENUMS for grow_state

  NO_CHANGE	= 0

  BIGGER	= 1

  SMALLER	= 2

   NSEOI_OCW2 = 00100001b

  PC_PIC	 = 20h

; direction constants

;          (bios key codes):

left    equ     4bh

right   equ     4dh

up      equ     48h

down    equ     50h

cur_dir db      right

wait_time dw    0

start:

     ; variables used for random

  food_x    DB 1					; cordinates of the next food

  food_y    DB 1					;

  attribute DB 13					; color of next food

  char      DB 41h				; char of next food

  food_type DB 1  	; type of next food,

				;0: '-' (makes snake smaller), o.w: ABC char

   ; variables for current food

  cur_food_x         DB 0

  cur_food_y         DB 0

  cur_food_type      DB 0

  cur_food_char      DB 0

  cur_food_attribute DB 0

  grow_state 	DB NO_CHANGE ; options: NO_CHANGE, BIGGER or SMALLER

  ezer_word  	DW 0

  ezer_byte  	DB 0

  ezer_byte2 	DB 0

  direction_for_next_cycle DB UP  	; contains the direction for next

						  ;cycle in main_loop

  one_before 	DB 0		; flag to use in 'erase_tail' (see there)

   .code

  mov ax,@data ; ds<-@data

  mov ds,ax

   ;call print_food

  ;call change_key_stroke_interrupt   ; changes the adress of routine resposible to response to key-stroke

                                     ; to perform 'update_direction'

  ;main_loop:

   ;   mov loop_counter,0

      ;call actions  ; performs all tasks for one movement: upadtes snake on screen, checks collision etc

; hide text cursor:

mov     ah, 1

mov     ch, 2bh

mov     cl, 0bh

int     10h

game_loop:

; === select first video page

mov     al, 0  ; page number.

mov     ah, 05h

int     10h

; === show new head:

mov     dx, snake[0]

; set cursor at dl,dh

mov     ah, 02h

int     10h

; print '*' at the location:

mov     al, '*'

mov     ah, 09h

mov     bl, 0eh ; attribute.

mov     cx, 1   ; single char.

int     10h

; === keep the tail:

mov     ax, snake[s_size * 2 - 2]

mov     tail, ax

call    move_snake

; === hide old tail:   solo la cabeza del gusanito cursor

mov     dx, tail

; set cursor at dl,dh       solo la cabeza del gusanito cursor

mov     ah, 02h

int     10h

; print ' ' at the location:    necesario para que no se cicle

mov     al, ' '

mov     ah, 09h

mov     bl, 0eh ; attribute.

mov     cx, 1   ; single char.

int     10h

check_for_key:

; === check for player commands:

mov     ah, 01h

int     16h

jz      no_key

mov     ah, 00h

int     16h

cmp     al, 1bh    ; esc - key?

je      stop_game  ;

mov     cur_dir, ah

no_key:

; === wait a few moments here:

; get number of clock ticks

; (about 18 per second)

; since midnight into cx:dx

mov     ah, 00h

int     1ah

cmp     dx, wait_time

jb      check_for_key

add     dx, 4

mov     wait_time, dx

; === eternal game loop:

jmp     game_loop

stop_game:

; show cursor back:

mov     ah, 1

mov     ch, 0bh

mov     cl, 0bh

int     10h

ret

  move_snake proc near

    ; set es to bios info segment:

mov     ax, 40h

mov     es, ax

  ; point di to tail

  mov   di, s_size * 2 - 2

  ; move all body parts

  ; (last one simply goes away)

  mov   cx, s_size-1

move_array:

  mov   ax, snake[di-2]

  mov   snake[di], ax

  sub   di, 2

  loop  move_array

  cmp     cur_dir, left

  je    move_left

cmp     cur_dir, right

  je    move_right

cmp     cur_dir, up

  je    move_up

cmp     cur_dir, down

  je    move_down

jmp     stop_move       ; no direction.

move_left:

  mov   al, b.snake[0]

  dec   al

  mov   b.snake[0], al

  cmp   al, -1

  jne   stop_move

  mov   al, es:[4ah]    ; col number.

  dec   al

  mov   b.snake[0], al  ; return to right.

  jmp   stop_move

  move_right:

  mov   al, b.snake[0]

  inc   al

  mov   b.snake[0], al

  cmp   al, es:[4ah]    ; col number.

  jb    stop_move

  mov   b.snake[0], 0   ; return to left.

  jmp   stop_move

  move_up:

  mov   al, b.snake[1]

  dec   al

  mov   b.snake[1], al

  cmp   al, -1

  jne   stop_move

  mov   al, es:[84h]    ; row number -1.

  mov   b.snake[1], al  ; return to bottom.

  jmp   stop_move

  move_down:

  mov   al, b.snake[1]

  inc   al

  mov   b.snake[1], al

  cmp   al, es:[84h]    ; row number -1.

  jbe   stop_move

  mov   b.snake[1], 0   ; return to top.

  jmp   stop_move

  ;loop_counter,0

  stop_move:

  ret

move_snake endp