Yel­low­tail is an inter­act­ive soft­ware sys­tem for the ges­tur­al cre­ation and per­form­ance of real-time abstract anim­a­tion. Yel­low­tail repeats a user­’s strokes end-over-end, enabling sim­ul­tan­eous spe­cific­a­tion of a line’s shape and qual­ity of move­ment. Each line repeats accord­ing to its own peri­od, pro­du­cing an ever-chan­ging and respons­ive dis­play of lively, worm-like textures.