焕然一新 huàn rán yì xīn - looks brand new ; eg after a new coat of paint, the house looks brand new . 家里涂了一层漆后，焕然一新，好像新房子一般。
一窍不通 yí qiào bù tōng - don't understand at all , eg. though he is a scientist, he can't understand arts at all. 他虽然是个博士， 对艺术却是一窍不通。
