game_snake:
   call .draw_screen
   call .detect_input

.draw_screen:
   call os_set_graphics_mode ; Clear screen
.draw_snake_loop:
   mov ax, [snake_x]
   mov [x_start], ax
   mov [x_end], ax

   mov bx, [snake_y]
   mov [y_start], bx
   mov [y_end], bx

   call os_draw_graphical_rectangle
   ret

; Player 1 movements
.up:
   mov dword [snake_direction], 0
   jmp .end_detect_input
.down:
   mov dword [snake_direction], 2
   jmp .end_detect_input
.left:
   mov dword [snake_direction], 3
   jmp .end_detect_input
.right:
   mov dword [snake_direction], 1
   jmp .end_detect_input

.move_up:
   mov dx, [snake_y]
   sub dx, 1
   mov [snake_y], dx
   ret
.move_down:
   mov dx, [snake_y]
   add dx, 1
   mov [snake_y], dx
   ret
.move_left:
   mov dx, [snake_x]
   sub dx, 1
   mov [snake_x], dx
   ret
.move_right:
   mov dx, [snake_x]
   add dx, 1
   mov [snake_x], dx
   ret

.move_snake:
   cmp dword [snake_direction], 0
   je .move_up
   cmp dword [snake_direction], 1
   je .move_right
   cmp dword [snake_direction], 2
   je .move_down
   ; Else it must be left
   jmp .move_left


.detect_input:
   call os_read_input
   cmp al, 08h
   je .finish

   ; Player 1
   cmp al, 77h       ; Pressed 'w' up
   je .up
   cmp al, 61h       ; Pressed 'a' left
   je .left
   cmp al, 73h       ; Pressed 's' down
   je .down
   cmp al, 64h       ; Pressed 'd' right
   je .right
.end_detect_input:
   call .move_snake
   call .draw_screen

   jmp .detect_input

.finish:
   call os_set_text_mode
   call os_start_cli


section .data:
   snake_x: dw 5
   snake_y: dw 5
   snake_direction: dw 1 ; 0=up, 1=right, 2=down, 3=left
   snake_length: dw 1