Keeping styles backward compatible can be a problem — particularly if you're using complex style with class variants.
让样式保持向后兼容可能有一定难度，尤其是在通过类变体应用复杂样式的情况下。
2
This imposes not merely a level of responsibility regarding backward compatibility, but a set of challenges relating to a demanding class of users.
这不仅意味着关于向后兼容的责任，而且是与大量不同类别的用户相关的挑战。
3
The SecurityManager class has, of course, been retained for backward compatibility, but its newer implementation delegates to the underlying AccessController.