Fangcaoxin (芳草心 "Fangfang, heart of grass") is a 1983 Chinese-language western-style opera or musical, and 1986 film.
The geju was based on the play Zhenqing jiayi (《真情假意》) by Ping Danhe which was in the repertoire of the Frontline Song and Dance Troupe (前线歌舞团).
The original play was collectively edited, with a new libretto by Xiang Tong (向彤) and He Zhaohua (何兆华) and then set to music by Wang Zujie (王祖皆 b.1949) and Zhang Zhuoya (张卓娅).
The plot concerns twin sisters Yunyun (媛媛) and Fangfang (芳芳) and their love for the engineer Yu Gang (于刚).
When Yu Gang's eyesight recovers Fangfang withdraws, and Yunyun returns to reclaim him, but her conscience drives her to admit the truth at their wedding.