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section .data
; example messages for later
message1 db "Hello, World!", 0xA
msg_len1 equ $ - message1
message2 db "Hello 2!", 0xA
msg_len2 equ $ - message2
; array of snake - 1000 thousand bytes means max length is 500
; x head is at snake[0]
; y head is at snake[1]
snake TIMES 250 db 0
snake_length db 2
; direction of the snake:
; 3
; 2 x 0
; 1
global direction
direction db 0
; delay of the game loop (0.5s in the beginning)
timespec dq 0
dq 500000000
section .rodata
; width and height of the playable area
; (without the borders)
global width
global height
width db 25
height db 10
section .text
extern fruit_x
extern fruit_y
extern spawn_fruit
extern draw_fruit
extern input
extern draw_border
extern write_byte
extern clear_screen
extern reset_cursor
extern move_cursor_right
extern move_cursor_down
extern hide_cursor
extern show_cursor
global _start
global exit
draw_snake:
push rbx
;;push r12
xor rdx, rdx
push rdx
call reset_cursor
pop rdx
_12:
mov bh, byte [snake+(2*rdx)]
mov bl, byte [snake+(2*rdx)+1]
_10:push rdx
call move_cursor_right
pop rdx
dec bh
cmp bh, 0
jnz _10
_11:push rdx
call move_cursor_down
pop rdx
dec bl
cmp bl, 0
jnz _11
push rdx
mov rax, 'x'
call write_byte
call reset_cursor
pop rdx
inc rdx
cmp dl, byte [snake_length]
jnz _12
;;pop r12
pop rbx
ret
move_snake:
;; TODO: loop this
mov ah, byte [snake]
mov al, byte [snake+1]
mov byte [snake+2], ah
mov byte [snake+3], al
;;
cmp byte [direction], 0
je _move_right
cmp byte [direction], 1
je _move_down
cmp byte [direction], 2
je _move_left
cmp byte [direction], 3
je _move_up
ret ; should not be accessed
_move_right:
inc byte [snake]
ret
_move_down:
inc byte [snake+1]
ret
_move_left:
dec byte [snake]
ret
_move_up:
dec byte [snake+1]
ret
check_eat_fruit:
mov ah, byte [fruit_x]
mov al, byte [fruit_y]
cmp byte [snake], ah
jz _check_y
ret
_check_y:
cmp byte [snake+1], al
jz _same_position
ret
_same_position:
; get longer
inc byte [snake_length]
call spawn_fruit
ret
_start:
call hide_cursor
mov byte [snake], 5
mov byte [snake+1], 5
mov byte [snake+2], 4
mov byte [snake+3], 5
call spawn_fruit
main_loop:
call clear_screen
call draw_border
call draw_snake
call draw_fruit
mov rax, 35
lea rdi, [timespec]
xor rsi, rsi
syscall
call input
call move_snake
call check_eat_fruit
jmp main_loop
exit: ; exit syscall with return code 0
call show_cursor
call clear_screen
mov rax, 60
xor rdi, rdi
syscall
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