Tile:
    + a center (Vector2) to position overlays and center pawns on it
    + multiple overlays (path,attack,wrecked,special terrains) centered on it
    + a stack of pawn
    - automatic overlays to show unit stack depth


Pawn:
    + a position (Vector3) to position overlays
    + an image
    + multiple overlays centered on it
    - a stack of moves to revert them


Board:
    - build possible assits List<Pawn / GridPoint2>
    - support different grid direction
        Board.Orientation offset
        inverted even/odd row scheme