text: #ifndef UI_H
  #define UI_H
  
  #include <stdlib.h>
  
  enum ui_screens { game_ui, main_menu_ui, unit_ui };
  struct game_screen {
      enum ui_screens* menu_state;
      int screen_num;
      int screen_cap;
  };
  
  extern struct game_screen screen_init (enum ui_screens menu);
  extern void screen_free (struct game_screen *screen);
  extern void screen_add (struct game_screen *screen, enum ui_screens ui);
  extern enum ui_screens screen_get (struct game_screen *screen);
  extern void screen_remove (struct game_screen *screen);
  extern int screen_removeif (struct game_screen *screen, enum ui_screens ui);
  extern int screen_toggle (struct game_screen *screen, enum ui_screens ui);
  
  #endif