n.難題；腦筋急轉(zhuǎn)彎
If you fill in squares correctly, options for the remaining ones are narrowed and it becomes easier to solve this brainteaser. 如果你正確地填充了方框，剩余的選擇范圍會(huì)縮小同時(shí)解決這個(gè)難題也就越簡單。
