and a few with Chen style, and the similarities with Yang-style weapons forms noted above, as well as similarities and differences on fundamental principles such as the Wu (Hao) style's focus on shifting and sinking vs. the Yang style's focus on shifting and twisting, though both styles contain all of those internal principles, just as all styles require the practitioner to clearly distinguish between "empty and solid" (, , xūshí) weighting during those movements. Shared principles aside, much of the Wu (Hao) approach is evidence of an independent evolution and can provide a new perspective for students of other styles. For example, in their forms where Yang stylists perform their signature moves of Commencing (qǐshì, , ) and Stroke Peacock's Tail's (, ) "péng lǚ jǐ àn" (), the Wu (Hao) forms instead perform Commencing and Lazily Bind the Cloak (lǎn zā yī, , ). In name that would seem to derive from the Chen style, but in this style that sequence is different from both Yang and Chen, with a unique approach to internal alignment. Beginning with Hao Weizhen, the internals of those movements have been named as: and these can also be applied to every posture in the form. Furthermore, Yao Jizu taught that all t'ai chi movements contain these principles: This is not to say that Wu (Hao)-style masters haven't from the beginning also taught the four directions "péng lǚ jǐ àn" and the four corners "cǎi liè zhǒu kào" (), at least in the context of pushing hands, as they have for example in the Pushing Hands Ditty () transmitted by Li Yiyu, in Wu Chengqing's recommendation to begin partner training with, as the Wu (Hao) style calls them, péng, lōu (), and zhǒu, and Hao Weizhen's mention of pushing hands in his advice to Sun Lutang, through more recent works such as Yao Jizu's chapter on pushing hands which shows the continued importance of the four directions and four corners by beginning with a basic push hands set in the pattern of "péng, lōu, zhǒu, àn". Yet for Wu (Hao) stylists, the most fundamental concept is "kai he". Other styles of tai chi and other internal martial arts also give attention to the importance of opening and closing in all movements, but Li Yiyu was the first to specifically call it kai he in his "Treatise on the Diagram of Substantial/Insubstantial and Opening/Closing", and Wu