As the opponent attacks, you become yin, pulling him off balance. But as he attempts to retreat, you become yang and uproot him. Yin and yang are kept in constant balance. Pa-Kua stresses the use of horizontal, circular movements and the open palm. But Hsing-l is based on solid footholds.
Movement is largely linear, expounding the strength of the straight line.
They rely on leverage to turn the opponents inner strength against himself. Since the attack coincides with the opponents moment of absolute helplessness, internal practitioners can frequently defeat an opponent without hurting him. Internal systems always embody some element of Chinese philosophy. Tai Chi Chuan is the yin and yang of boxing. Pa-Kua is the eight trigrams boxing.