1 files changed, 159 insertions, 0 deletions
diff --git a/src/main.asm b/src/main.asm
new file mode 100644
index 0000000..170f6a2
--- /dev/null
+++ b/src/main.asm
@@ -0,0 +1,159 @@
+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 1000 db 0
+    snake_length dw 1
+
+    ; position of the fruit
+    fruit_x db 0
+    fruit_y db 0
+
+    ; direction of the snake:
+    ;   3
+    ; 2 x 0
+    ;   1
+    global direction
+    direction db 0
+
+    timespec dq 0 
+             dq 500000000
+
+section .rodata
+    ; width and height of the playable area
+    ; (without the borders)
+    global width
+    global height
+    width db 70
+    height db 30
+
+section .text
+    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
+    call reset_cursor
+    mov bh, byte [snake]
+    mov bl, byte [snake+1]
+
+_10:call move_cursor_right
+    dec bh
+    cmp bh, 0
+    jnz _10
+_11:call move_cursor_down
+    dec bl
+    cmp bl, 0
+    jnz _11
+
+    mov rax, 'x'
+    call write_byte
+
+    pop rbx
+    call reset_cursor
+    ret
+
+move_snake:
+    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
+
+_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
+
+fruit_position:
+
+    ; x position
+    rdtsc
+    shr ax, 5
+    div byte [width]
+    mov byte [fruit_x], ah
+;; TODO
+    rdtsc
+    shr ax, 5
+    div byte [height]
+    mov byte [fruit_y], ah
+
+    ret
+
+draw_fruit:
+    push rbx
+    call reset_cursor
+    mov bh, byte [fruit_x]
+    mov bl, byte [fruit_y]
+
+_30:call move_cursor_right
+    dec bh
+    cmp bh, 0
+    jnz _30
+_31:call move_cursor_down
+    dec bl
+    cmp bl, 0
+    jnz _31
+
+    mov rax, '*'
+    call write_byte
+
+    pop rbx
+    call reset_cursor
+    ret
+
+_start:
+    call hide_cursor
+    mov byte [snake], 5
+    mov byte [snake+1], 5
+    call fruit_position
+
+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
+
+    jmp main_loop
+
+exit: ; exit syscall with return code 0
+    call show_cursor
+    mov rax, 60                     
+    xor rdi, rdi                    
+    syscall