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snake.asm
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snake.asm
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; NASM
; nasm -o snake.com -fbin snake.asm
%define VGA_MEM 0A000H ; video memory
%define SCR_MEM 09000H ; last 64kB segment
%define FONT_SEG 0F000H ; ROM-Font segment
%define FONT_OFF 0FA6EH ; ROM-Font offset
%define TRANSPARENT_COLOR 0
%define KEY_ESC 1
%define KEY_UP 72
%define KEY_DOWN 80
%define KEY_LEFT 75
%define KEY_RIGHT 77
%define KEY_A 30
%define KEY_P 25
CPU 186
BITS 16
ORG 100H
JMP main
; keyboard routines
keyboard_int:
STI
PUSH AX
IN AL,60H ; get key from keyboard port
MOV [CS:lastkey],AL
POP AX
PUSH AX
PUSH CX
MOV AX,0
MOV AL,[CS:lastkey]
CMP AL,128 ; check keyboard data (pressed or not)
JNAE check_keys_1
SUB AL,128
MOV CL,0
JMP check_keys_2
check_keys_1:
MOV CL,1
check_keys_2:
MOV BX,key
ADD BX,AX
MOV [CS:BX],CL
POP CX
POP AX
PUSH AX
MOV AL,20H ; send end of irq
OUT 20H,AL
POP AX
CLI
IRET
install_keyboard:
MOV AX,3509H ; get old keyboard int proc
INT 21H
MOV [CS:old_keyboard_int],BX
MOV [CS:old_keyboard_int + 2],ES
MOV AX,2509H ; set new keyboard int proc
MOV DX,keyboard_int
PUSH DS
PUSH CS
POP DS
INT 21H
POP DS
RET
remove_keyboard:
MOV AX,2509H ; restore old keyboard proc
LDS DX,[CS:old_keyboard_int]
INT 21H
RET
wait_for_any_key:
MOV BYTE [lastkey],0
MOV DL,[lastkey]
wait_for_any_key_1:
CMP DL,[lastkey]
JE wait_for_any_key
RET
;-------
; timer routines
timer_int:
STI
MOV BYTE [CS:can_update],1 ; update game
INC BYTE [CS:timer_counter]
CMP BYTE [CS:timer_counter],18
JE timer_int_reset_delay
JMP timer_int_end
timer_int_reset_delay:
MOV BYTE [CS:timer_delay],0
MOV BYTE [CS:timer_counter],0
timer_int_end:
CLI
IRET
install_timer:
MOV AX,351CH ; get old timer int proc
INT 21H
MOV [CS:old_timer_int],BX
MOV [CS:old_timer_int + 2],ES
MOV AX,251CH ; set new timer int proc
MOV DX,timer_int
PUSH DS
PUSH CS
POP DS
INT 21H
POP DS
RET
remove_timer:
MOV AX,251CH ; restore old timer proc
LDS DX,[CS:old_timer_int]
INT 21H
RET
;-------
; gfx routines
init13h:
MOV AX,0013H ; set 320x200 8bit video mode
INT 10H
RET
close13h:
MOV AX,0003H ; restore text mode
INT 10H
RET
vsync: ; wait for end of screen updating
PUSH AX
PUSH DX
MOV DX,03DAH
vsync_1:
IN AL,DX
TEST AL,0
JNE vsync_1
POP DX
POP AX
RET
set_palette:
PUSH AX
PUSH BX
PUSH CX
PUSH DX
MOV AX,0
MOV BX,palette ; load palette adress to BX
MOV CX,256 ; 256 colors (8bit)
set_palette_1:
PUSH AX
MOV DX,03C8H ; set first VGA DAC port
OUT DX,AL ; send color num (AL) to VGA DAC
INC DX ; set next port
MOV AL,[BX] ; send RGB and increment BX pointer
OUT DX,AL
INC BX
MOV AL,[BX]
OUT DX,AL
INC BX
MOV AL,[BX]
OUT DX,AL
INC BX
POP AX
INC AL ; increment color num
LOOP set_palette_1
POP DX
POP BX
POP CX
POP AX
RET
draw_screen: ; move data from 9000h to A000h segment
CALL vsync
PUSH DS
PUSH ES
PUSH AX
PUSH CX
PUSH DI
MOV AX,SCR_MEM
MOV DS,AX
MOV AX,VGA_MEM
MOV ES,AX
MOV CX,64000
draw_screen_1:
MOV DI,CX
DEC DI
MOV AL,[DS:DI]
MOV [ES:DI],AL
LOOP draw_screen_1
POP DI
POP CX
POP AX
POP ES
POP DS
RET
clear_screen: ; clear screen buffer, CL - color
PUSH ES
PUSH AX
PUSH DI
MOV AX,SCR_MEM
MOV ES,AX
MOV AL,CL
MOV CX,64000
clear_screen_1:
MOV DI,CX
DEC DI
MOV [ES:DI],AL
LOOP clear_screen_1
POP DI
POP AX
POP ES
RET
putpixel: ; AX - x, BX - y, CL - color
PUSH AX
PUSH BX
PUSH CX
PUSH DI
PUSH ES
PUSH AX
MOV AX,BX
MOV BX,320
MUL BX
POP BX
ADD AX,BX
MOV DI,AX
MOV AX,SCR_MEM
MOV ES,AX
MOV [ES:DI],CL
POP ES
POP DI
POP CX
POP BX
POP AX
RET
getpixel: ; AX - x, BX - y, return: CL - color
PUSH AX
PUSH BX
PUSH DI
PUSH ES
PUSH AX
MOV AX,BX
MOV BX,320
MUL BX
POP BX
ADD AX,BX
MOV DI,AX
MOV AX,SCR_MEM
MOV ES,AX
MOV CL,[ES:DI]
POP ES
POP DI
POP BX
POP AX
RET
draw_sprite: ; SX - x, SY - y, SW - width, SH - height, BX - data
PUSH AX
PUSH BX
PUSH CX
PUSH DX
PUSH ES
PUSH DI
MOV AX,SCR_MEM
MOV ES,AX
MOV AX,[SY]
MOV CX,[SH]
draw_sprite_y_axis:
PUSH CX
PUSH AX
MOV DX,320
MUL DX
ADD AX,[SX]
MOV DI,AX
MOV CX,[SW]
draw_sprite_x_axis:
MOV AL,[BX]
MOV [ES:DI],AL
INC DI
INC BX
LOOP draw_sprite_x_axis
POP AX
INC AX
POP CX
LOOP draw_sprite_y_axis
POP DI
POP ES
POP DX
POP CX
POP BX
POP AX
RET
draw_transparent_sprite: ; SX - x, SY - y, SW - width, SH - height, BX - data
PUSH AX
PUSH BX
PUSH CX
PUSH DX
PUSH ES
PUSH DI
MOV AX,SCR_MEM
MOV ES,AX
MOV AX,[SY]
MOV CX,[SH]
draw_transparent_sprite_y_axis:
PUSH CX
PUSH AX
MOV DX,320
MUL DX
ADD AX,[SX]
MOV DI,AX
MOV CX,[SW]
draw_transparent_sprite_x_axis:
MOV AL,[BX]
CMP AL,TRANSPARENT_COLOR
JE draw_transparent_sprite_x_next
MOV [ES:DI],AL
draw_transparent_sprite_x_next
INC DI
INC BX
LOOP draw_transparent_sprite_x_axis
POP AX
INC AX
POP CX
LOOP draw_transparent_sprite_y_axis
POP DI
POP ES
POP DX
POP CX
POP BX
POP AX
RET
hline: ; PX1 - x1, PY1 - y, PX2 - x2, PCL - color
PUSH ES
PUSH DI
PUSH AX
PUSH BX
PUSH CX
MOV AX,SCR_MEM
MOV ES,AX
MOV AX,[PY1]
MOV BX,320
MUL BX
ADD AX,[PX1]
MOV DI,AX
MOV AL,[PCL]
MOV CX,[PX2]
SUB CX,[PX1]
hline_1:
MOV BYTE [ES:DI],AL
INC DI
LOOP hline_1
POP CX
POP BX
POP AX
POP DI
POP ES
RET
vline: ; PX1 - x, PY1 - y1, PY2 - y2, PCL - color
PUSH ES
PUSH DI
PUSH AX
PUSH BX
PUSH CX
MOV AX,SCR_MEM
MOV ES,AX
MOV AX,[PY1]
MOV BX,320
MUL BX
ADD AX,[PX1]
MOV DI,AX
MOV AL,[PCL]
MOV CX,[PY2]
SUB CX,[PY1]
vline_1:
MOV [ES:DI],AL
ADD DI,320
LOOP vline_1
POP CX
POP BX
POP AX
POP DI
POP ES
RET
rect: ; PX1 - x1, PY1 - y1, PX2 - x2, PY2 - y2, PCL - color
PUSH AX
PUSH BX
PUSH CX
CALL hline
CALL vline
MOV AX,[PY1]
MOV BX,[PY2]
MOV [PY1],BX
CALL hline
MOV [PY1],AX
MOV AX,[PX1]
MOV BX,[PX2]
MOV [PX1],BX
CALL vline
MOV [PX1],AX
MOV AX,[PX2]
MOV BX,[PY2]
MOV CL,[PCL]
CALL putpixel
POP CX
POP BX
POP AX
RET
rectfill:
PUSH AX
PUSH CX
MOV AX,[PY1]
MOV CX,[PY2]
SUB CX,[PY1]
rectfill_1:
CALL hline
INC WORD [PY1]
LOOP rectfill_1
MOV [PY1],AX
CALL rect
POP CX
POP AX
RET
draw_char_mask: ; AX - x, BX - y, CL - color, CH - char mask
PUSH AX
PUSH BX
PUSH CX
PUSH DX
MOV DX,CX
MOV CX,8
draw_char_mask_1:
PUSH CX
SHL DH,1
JNC draw_char_mask_2
PUSH DX
MOV CL,DL
CALL putpixel
POP DX
draw_char_mask_2:
POP CX
INC AX
LOOP draw_char_mask_1
POP DX
POP CX
POP BX
POP AX
RET
draw_char: ; AX - x, BX - y, CL - color, CH - char
PUSH AX
PUSH BX
PUSH CX
PUSH DX
PUSH ES
PUSH DI
PUSH AX
MOV AX,FONT_SEG
MOV ES,AX
MOV AX,FONT_OFF
MOV DI,AX
MOV AX,0
MOV AL,CH
SHL AX,3
ADD DI,AX
POP AX
MOV DX,CX
MOV CX,8
draw_char_1:
PUSH CX
MOV CX,DX
MOV CH,[ES:DI]
CALL draw_char_mask
INC DI
INC BX
POP CX
LOOP draw_char_1
POP DI
POP ES
POP DX
POP CX
POP BX
POP AX
RET
draw_integer: ; AX - x, BX - y, CL - color, DX - integer
PUSH AX
PUSH BX
PUSH CX
PUSH DX
PUSH DI
MOV DI,10000
MOV [draw_integer_cl],CL
MOV CX,5
draw_integer_1:
PUSH CX
PUSH AX
PUSH BX
PUSH DX
MOV AX,DX
XOR DX,DX
MOV BX,DI
DIV BX
MOV CH,AL
MUL BX
POP DX
SUB DX,AX
POP BX
POP AX
ADD CH,'0'
MOV CL,[draw_integer_cl]
CALL draw_char
ADD AX,8
PUSH AX
PUSH BX
PUSH DX
MOV AX,DI
MOV BX,10
XOR DX,DX
DIV BX
MOV DI,AX
POP DX
POP BX
POP AX
POP CX
LOOP draw_integer_1
POP DI
POP DX
POP CX
POP BX
POP AX
RET
draw_integer_cl DB 0 ; color (temp)
draw_text: ; AX - x, BX - y, CL - color, DX - data
PUSH AX
PUSH BX
PUSH CX
PUSH DX
XCHG BX,DX
draw_text_1:
MOV CH,[BX]
INC BX
XCHG BX,DX
CALL draw_char
ADD AX,8
XCHG BX,DX
CMP BYTE [BX],0
JNE draw_text_1
POP DX
POP CX
POP BX
POP AX
RET
;-------
; program code
random_init:
PUSH AX
PUSH CX
PUSH DX
MOV AH,2CH
INT 21H
MOV [random_seed],DX
POP DX
POP CX
POP AX
RET
random_gen: ; return: CL - random byte
MOV CX,[random_seed]
IMUL CX,13A7H
INC CX
MOV [random_seed],CX
MOV CL,CH
MOV CH,0
RET
random: ; AL - max random number
CALL random_gen
CMP CL,AL
JAE random
RET
random_seed DW 0 ; seed
delay: ; AX - hund. seconds (1/100 s)
MOV BYTE [timer_delay],1
delay_1:
CMP BYTE [timer_delay],0
JNE delay_1
RET
sound_on:
PUSH AX
MOV AL,0B6H
OUT 43H,AL
MOV AX,11930
OUT 42H,AL
MOV AL,AH
OUT 42H,AL
IN AL,61H
OR AL,3
OUT 61H,AL
POP AX
RET
sound_off:
PUSH AX
IN AL,61H
AND AL,252
OUT 61H,AL
POP AX
RET
move_snake:
PUSH AX
PUSH BX
PUSH CX
PUSH DX
CMP BYTE [snake_vector],0
JE move_snake_end
MOV CX,[snake_len]
DEC CX
move_snake_1:
PUSH CX
DEC CX
MOV BX,snake
MOV AX,CX
MOV CX,4
MUL CX
ADD BX,AX
MOV AX,[BX]
MOV CX,[BX + 2]
MOV [BX + 4],AX
MOV [BX + 6],CX
POP CX
LOOP move_snake_1
CMP BYTE [snake_vector],1
JE move_snake_up
CMP BYTE [snake_vector],2
JE move_snake_down
CMP BYTE [snake_vector],3
JE move_snake_left
CMP BYTE [snake_vector],4
JE move_snake_right
move_snake_up:
SUB WORD [snake + 2],5
JMP move_snake_vector_end
move_snake_down:
ADD WORD [snake + 2],5
JMP move_snake_vector_end
move_snake_left:
SUB WORD [snake],5
JMP move_snake_vector_end
move_snake_right:
ADD WORD [snake],5
JMP move_snake_vector_end
move_snake_vector_end:
move_snake_end:
POP DX
POP CX
POP BX
POP AX
RET
set_snakes_vector:
PUSH AX
CMP AL,1
JE set_snakes_vector_up
CMP AL,2
JE set_snakes_vector_down
CMP AL,3
JE set_snakes_vector_left
CMP AL,4
JE set_snakes_vector_right
JMP set_snakes_vector_end
set_snakes_vector_up:
CMP BYTE [snake_vector],2 ; if not down
JE set_snakes_vector_up_1
MOV BYTE [snake_vector],1 ; set up
set_snakes_vector_up_1:
JMP set_snakes_vector_end
set_snakes_vector_down:
CMP BYTE [snake_vector],1 ; if not up
JE set_snakes_vector_down_1
MOV BYTE [snake_vector],2 ; set down
set_snakes_vector_down_1:
JMP set_snakes_vector_end
set_snakes_vector_left:
CMP BYTE [snake_vector],4 ; if not right
JE set_snakes_vector_left_1
CMP BYTE [snake_vector],0 ; if not 'no move'
JE set_snakes_vector_left_1
MOV BYTE [snake_vector],3 ; set left
set_snakes_vector_left_1:
JMP set_snakes_vector_end
set_snakes_vector_right:
CMP BYTE [snake_vector],3 ; if not left
JE set_snakes_vector_right_1
MOV BYTE [snake_vector],4 ; set right
set_snakes_vector_right_1:
JMP set_snakes_vector_end
set_snakes_vector_end:
POP AX
RET
reset_snake:
MOV WORD [snake + 14],60
MOV WORD [snake + 12],25
MOV WORD [snake + 10],60
MOV WORD [snake + 8],30
MOV WORD [snake + 6],60
MOV WORD [snake + 4],35
MOV WORD [snake + 2],60
MOV WORD [snake],40
MOV WORD [snake_len],4
MOV BYTE [snake_vector],0
RET
reset_food:
PUSH AX
PUSH BX
PUSH CX
; random food x
MOV AL,58 ; max area width / 5
CALL random
MOV AH,0
MOV AL,CL
MOV BX,5
MUL BX
ADD AX,5
MOV [snakes_food_x],AX
; random food y
MOV AL,35 ; max area height / 5
CALL random
MOV AH,0
MOV AL,CL
MOV BX,5
MUL BX
ADD AX,20
MOV [snakes_food_y],AX
POP CX
POP BX
POP AX
RET
increase_snake: ; snake++ :), new head = food position
PUSH AX
PUSH BX
PUSH CX
PUSH DX
MOV CX,[snake_len]
increase_snake_1:
PUSH CX
DEC CX
MOV BX,snake
MOV AX,CX
MOV CX,4
MUL CX
ADD BX,AX
MOV AX,[BX]
MOV CX,[BX + 2]
MOV [BX + 4],AX
MOV [BX + 6],CX
POP CX
LOOP increase_snake_1
MOV AX,[snakes_food_x]
MOV [snake],AX
MOV AX,[snakes_food_y]
MOV [snake + 2],AX
INC WORD [snake_len]
MOV AX,[snake_len]
CMP AX,[snake_max_len] ; if snake_len == snake_max_len then print winner msg and quit
JE increase_snake_max_len
JMP increase_snake_end
increase_snake_max_len:
CALL winner
increase_snake_end:
POP DX
POP CX
POP BX
POP AX
RET
detect_collisions: ; detect collisions beetwen objects
PUSH AX
PUSH BX
PUSH CX
PUSH DX
; detect head and food collision
MOV AX,[snakes_food_x]
CMP AX,[snake] ; compare food x with head x
JNE detect_collisions_1
MOV AX,[snakes_food_y]
CMP AX,[snake + 2] ; compare food y with head y
JNE detect_collisions_1
; add points and increase snake
ADD WORD [score],10 ; add 10 points :)
CALL increase_snake
CALL reset_food
detect_collisions_1:
; detect collision with border and decrase lives
CMP WORD [snake],0 ; coll. with left border
JE detect_collisions_dead
CMP WORD [snake],320 - 5 ; coll. with right border
JE detect_collisions_dead
CMP WORD [snake + 2],15 ; coll. with top border
JE detect_collisions_dead
CMP WORD [snake + 2],200 - 5 ; coll. with bottom border
JE detect_collisions_dead
; detect head collision with body
MOV BX,snake
ADD BX,8 ; jump to next x&y
MOV AX,[snake]
MOV DX,[snake + 2]
MOV CX,[snake_len]
DEC CX
detect_collisions_head_with_body:
CMP AX,[BX]
JNE detect_collisions_head_with_body_next
CMP DX,[BX + 2]
JE detect_collisions_dead
detect_collisions_head_with_body_next:
ADD BX,4
LOOP detect_collisions_head_with_body
; if everything is ok the jump to the end
JMP detect_collisions_end
detect_collisions_dead:
CALL reset_snake
CALL reset_food
DEC BYTE [live_counter]
MOV AX,1000
CALL draw_screen
CALL sound_on
CALL delay
CALL sound_off
detect_collisions_end:
POP DX
POP CX
POP BX
POP AX
RET
main:
CALL init13h
CALL install_keyboard
CALL install_timer
CALL set_palette
CALL random_init
; setup snake
CALL reset_snake
CALL reset_food
game_loop:
; synchronize game
CMP BYTE [can_update],1
JNE game_loop
MOV BYTE [can_update],0
; clear screen buffer
MOV CL,0
CALL clear_screen
; draw frame
MOV BX,sprite_frame_box
MOV WORD [SW],5
MOV WORD [SH],5
; draw top frame
MOV WORD [SX],0
MOV WORD [SY],0
MOV CX,320 / 5
draw_frame_top:
CALL draw_sprite
ADD WORD [SX],5
LOOP draw_frame_top
; draw bottom frame
MOV WORD [SX],0
MOV WORD [SY],200 - 5
MOV CX,320 / 5
draw_frame_bottom:
CALL draw_sprite
ADD WORD [SX],5
LOOP draw_frame_bottom
; draw left frame
MOV WORD [SX],0
MOV WORD [SY],0
MOV CX,200 / 5
draw_frame_left:
CALL draw_sprite
ADD WORD [SY],5
LOOP draw_frame_left
; draw_frame_right
MOV WORD [SX],320 - 5
MOV WORD [SY],0
MOV CX,200 / 5
draw_frame_right:
CALL draw_sprite
ADD WORD [SY],5
LOOP draw_frame_right
; draw top bar
MOV WORD [PX1],5
MOV WORD [PY1],5
MOV WORD [PX2],320 - 5 - 1
MOV WORD [PY2],5 + 13 + 1
MOV BYTE [PCL],43
CALL rectfill
MOV BYTE [PCL],53
CALL rect
; draw logo
MOV BX,sprite_logo
MOV WORD [SX],320 / 2 - 54 / 2
MOV WORD [SY],7
MOV WORD [SW],54
MOV WORD [SH],11
CALL draw_transparent_sprite
; draw live counter
MOV BX,sprite_snake_live_0
MOV WORD [SW],13
MOV WORD [SH],11
MOV WORD [SY],7
MOV WORD [SX],320 - 5 - 18
CALL draw_transparent_sprite
MOV WORD [SX],320 - 5 - 18 - 18
CALL draw_transparent_sprite
MOV WORD [SX],320 - 5 - 18 - 18 - 18
CALL draw_transparent_sprite
MOV BX,sprite_snake_live_1
CMP BYTE [live_counter],0 ; if game over
JE counter_game_over
JMP counter_draw_live
counter_game_over:
CALL game_over
counter_draw_live:
MOV WORD [SX],320 - 5 - 18
CALL draw_transparent_sprite
CMP BYTE [live_counter],2
JB draw_live_counter_end
MOV WORD [SX],320 - 5 - 18 - 18
CALL draw_transparent_sprite
CMP BYTE [live_counter],3