result = {}
    for dimension, a, b, center, size in (("x", "left", "right", "center_x", "width"), ("y", "top", "bottom", "center_y", "height)):
        assert 2 == sum(1 for name in (a, b, center, size) if name in kwargs), f"{dimension} coordinates are overspecified or underspecified"
        if size in kwargs and a in kwargs:
            result[b] = kwargs[size] + kwargs[a]
        elif b in kwargs and size in kwargs:
            result[a] = kwargs[b] - kwargs[size]
        elif center in kwargs and b in kwargs:
            result[a] = 2*kwargs[center] - kwargs[b]
        elif center in kwargs and a in kwargs:
            result[b] = 2*kwargs[center] - kwargs[a]
        elif center in kwargs and size in kwargs:
            result[a] = kwargs[center] - kwargs[size]/2
            result[b] = kwargs[center] + kwargs[size]/2
        if a in kwargs: result[a] = kwargs[a]
        if b in kwargs: result[b] = kwargs[b]
    return Rect(**result)