274 lines
8.9 KiB
NASM
274 lines
8.9 KiB
NASM
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; ;;
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;; ;;;;;; ;;;;;; ;;
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;; ;; ;; ;; ;;
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;; ;; ;; ;;;;;; ;;; ;; ;; ;; ;; ;;; ;; ;; ;;;;;; ;;
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;; ;;;;;; ;; ;; ;; ;; ;;;;;;; ;;; ;; ;; ;; ;; ;; ;; ;;
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;; ;; ;; ;;;;; ;; ;; ;; ;; ;; ; ;; ;; ;; ;;;; ;;;;;; ;;
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;; ;; ;; ;; ;;;;;;; ;; ;; ;; ;;; ;;;;;;; ;; ;; ;; ;;
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;; ;; ;; ;;;;;; ;; ;; ;;;;;; ;;;;;; ;; ;; ;; ;; ;; ;; ;;;;;; ;;
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;; ;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; ;;
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;; Snake like game writen in x86 real mode assembly. ;;
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;; Copyright (C) 2014 Piotr Majkrzak <petrol.91@gmail.com> ;;
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;; ;;
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;; This program is free software: you can redistribute it and/or modify ;;
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;; it under the terms of the GNU General Public License as published by ;;
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;; the Free Software Foundation, either version 3 of the License, or ;;
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;; (at your option) any later version. ;;
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;; ;;
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;; This program is distributed in the hope that it will be useful, ;;
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;;
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;;
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;; GNU General Public License for more details. ;;
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;; ;;
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;; You should have received a copy of the GNU General Public License ;;
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;; along with this program. If not, see <http://www.gnu.org/licenses/>. ;;
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;; ;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; ;;
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;; ;;
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;; About ;;
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;;------- ;;
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;; ;;
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;; This game is written in Intel's x86 real mode assembly. It is designed ;;
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;; to fit in the boot sector, so it must have at most 510 bytes. Therefore, ;;
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;; it has very limited functionalities and spaghetti code. You are able to ;;
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;; change snake's head direction, eat fruits and restart the game. ;;
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;; ;;
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;; ;;
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;; Assembly ;;
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;;---------- ;;
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;; ;;
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;; To build this code you need to have NASM installed, you can get it from ;;
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;; this website: (http://www.nasm.us/). ;;
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;; Execute following command: ;;
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;; ;;
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;; nasm -fbin snake.asm -o snake.bin ;;
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;; ;;
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;; ;;
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;; Launch ;;
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;;-------- ;;
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;; ;;
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;; Now you have `snake.bin` file, which can be installed or loaded into ;;
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;; virtual machine like QEMU, which you can get from (www.qemu.org/). ;;
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;; ;;
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;; qemu-system-i386 snake.bin ;;
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;; ;;
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;; ;;
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;; Gameplay ;;
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;;---------- ;;
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;; ;;
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;; When the game will be launched, you will see huge green rectangle in the ;;
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;; middle of the screen. Snake is hidden now in top left corner. To move it ;;
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;; you should set its head direction, using arrow keys. If you are stuck or ;;
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;; you just want to restart the game, you should press space bar. ;;
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;; ;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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[org 0x1000]
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%DEFINE EMPTY 0b0000_0000
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%DEFINE SNAKE 0b0000_0001
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%DEFINE FRUIT 0b0000_0010
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%DEFINE EATEN 0b0000_0100
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%DEFINE WRECK 0b0000_1000
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%DEFINE DIRUP 0b0001_0000
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%DEFINE DIRDO 0b0010_0000
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%DEFINE DIRLE 0b0100_0000
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%DEFINE DIRRI 0b1000_0000
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%define map(i) byte [es:i]
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%define head word [es:1024]
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%define tail word [es:1026]
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%define fpos word [es:1028]
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%define ftim word [es:1030]
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%define rand word [es:1032]
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db 0x7A
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init:
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.random:
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mov ah, 0
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int 0x1A
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mov rand, dx
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.display:
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mov ah, 0x00
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mov al, 0x13
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int 0x10
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.interrupt:
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mov [fs:0x08*4], word timer
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mov [fs:0x08*4+2], ds
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mov [fs:0x09*4], word keyboard
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mov [fs:0x09*4+2], ds
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main:
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hlt
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jmp main
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;; () -> (ax); ax,cx,dx
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random:
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mov ax, rand
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mov dx, 7993
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mov cx, 9781
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mul dx
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add ax, cx
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mov rand, ax
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ret
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;; (si) -> (di,ah:al) ; cx,dx
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movement:
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mov cl, map(si)
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mov ax, si
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mov dl, 32
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div dl
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test cl, DIRUP
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jz $+4
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dec al
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test cl, DIRDO
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jz $+4
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inc al
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test cl, DIRLE
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jz $+4
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dec ah
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test cl, DIRRI
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jz $+4
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inc ah
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and al, 31
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and ah, 31
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movzx di, al
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rol di, 5
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movzx cx, ah
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add di,cx
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ret
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keyboard:
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in al, 0x60
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mov bx, head
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mov ah, map(bx)
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cmp al, 0x39
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jne $+12
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mov cx, 1032
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mov al, 0
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mov di, 0
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rep stosb
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and ah, 0x0F
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cmp al, 0x48
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jne $+5
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or ah, DIRUP
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cmp al, 0x50
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jne $+5
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or ah, DIRDO
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cmp al, 0x4b
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jne $+5
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or ah, DIRLE
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cmp al, 0x4d
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jne $+5
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or ah, DIRRI
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test ah, 0xF0
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jz $+4
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mov map(bx), ah
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mov al, 0x61
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out 0x20, al
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iret
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timer:
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.tick_rtc:
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int 0x70
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.move_head:
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mov si, head
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call movement
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mov ah, map(di)
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mov al, map(si)
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test al, WRECK
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jz $+3
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iret
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test ah, SNAKE|EATEN
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jz $+7
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mov map(si), WRECK
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iret
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test ah, FRUIT
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jz $+20
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mov ftim, 0
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mov fpos, -1
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mov bl, EATEN
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jmp $+4
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mov bl, SNAKE
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and al, 0xF0
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or bl, al
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mov map(di), bl
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mov head, di
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.move_tail:
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mov si, tail
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call movement
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mov al, map(si)
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test al, SNAKE
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jz $+11
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mov map(si), EMPTY
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mov tail, di
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jnz $+9
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and al, 0xF0
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or al, SNAKE
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mov map(si), al
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.move_fruit:
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cmp ftim, 0
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jne $+42
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mov bx, fpos
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mov map(bx), EMPTY
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call random
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mov bx, ax
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and bx, 1023
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cmp map(bx), EMPTY
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jne $-13
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mov map(bx), FRUIT
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mov fpos, bx
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mov ftim, 64
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dec ftim
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.redraw:
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mov cx, 0
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mov ax, cx
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mov dl, 32
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div dl
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mov bx, ax
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movzx ax, bl
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add ax, 9
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mov dx, 320
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mul dx
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movzx dx, bh
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add ax, dx
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add ax, 24
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mov dx, 4
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mul dx
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mov di, cx
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mov dl, map(di)
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and dl, 0x0F
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cmp dl, EMPTY
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jne $+8
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mov ebx, 0x02020202
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cmp dl, SNAKE
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jne $+8
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mov ebx, 0x01010101
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cmp dl, FRUIT
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jne $+8
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mov ebx, 0x04040404
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cmp dl, EATEN
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jne $+8
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mov ebx, 0x05050505
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mov di, ax
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mov [gs:di],ebx
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add di, 320
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mov [gs:di],ebx
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add di, 320
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mov [gs:di],ebx
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add di, 320
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mov [gs:di],ebx
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inc cx
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cmp cx, 1024
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jne .redraw+3
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iret
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times 510-($-$$) db 0
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dw 0AA55h
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