钩心斗角 — “To scheme against each other”

During the Tang Dynasty, the poet Du Mu was deeply moved by the late Tang emperors' extravagant construction projects and decadent lifestyle. He wrote 'The Epang Palace Rhapsody' (阿房宫赋) to satirize the rulers of his time. The essay vividly describes the magnificent splendor of the Epang Palace, with a passage that reads: 'Every five steps a tower, every ten steps a pavilion. The corridors wind and turn, the eaves jut out like beaks. Each structure embraces the terrain, with interlocking designs and competing eaves (钩心斗角).'

The idiom originally depicted the intricate, complex, and seemingly 'contending' architectural structures of the palace, implying their elaborate and ingenious design. Later, it evolved to metaphorically describe people using all their wits in overt and covert struggles, scheming against each other.