TODO:
    - turret aiming sound
    - battle description
    - moving cloudy sky overlay
    - Rules
        - 9.6 improved position as trait on Unit ??
        - 6.3 Russian mass activation
        - 8.6 Russian fire restrictions

NEXT:
    - option rotate head/pawn
    - support different board layout
        - north orientation
        - hex orientation
        - inverted even/odd row scheme
    - automatic overlays to show unit stack depth