Emacs的类似矩阵的空闲动画

As is, my emacs is set up to show green text on a black background. On seeing it, a friend remarked that I just took it because of the Matrix-like appearance it gives. So, now what I want to do is implement an idle animation for it where, like in the matrix, changing text falls down the screen. Like in the zone out functions, it should run after emacs has been idle for a while. How would this be done?As is, my emacs is set up to show green text on