Yuri Possokhov’s “Classical Symphony” has been declared breakthrough choreography for the Choreographer in Residence at the San Francisco Ballet. Although grounded in classical ballet, the movement is joyfully unique. This is a choreographer who understands his medium and is unafraid to test the limits of the dancers’ abilities. “Classical Symphony” is sometimes lovely, usually driving, frequently unexpected, and always incredibly demanding. From the breathtaking side-lighting on the dancers in tableau when the curtain opens to the final notes of the music, the ballet will captivate you. It is busy, filled with counterpoint, built around chaotic moments that suddenly evolve into unanticipated, inspired designs. The dancers are dancing on the edge, accelerating, braking, sliding, and only their technical expertise holds them there, keeping them from tumbling over the precipice. They are visibly elated by their success at mastering the difficulties of the choreography. The casting of Jackie Nash and Christian Clark seems to be the only possible choice for the central roles: both have attained a new level of maturity and confidence this year. The costumes are whimsical take-offs on classical tutus and tunics, and, like the movement, seem to be science fiction interpretations that only enhance the choreographer’s intent. This ballet alone is worth the price of admission, and it is worth splurging to sit in the center to have the best view of the intricate spatial designs.