Lisp on Pocket Station

I implemented a Lisp interpreter for Pocket Station. Pocket Station is a mobile game console by SONY. It has a ARM7T CPU, 2KB SRAM, and 32x32 dot monochrome LCD. We can type alphabet letters with UP botton and DOWN botton, and type parentheses with ENTER UP and ENTER DOWN buttons. We also can use auto complete for symbols with ENTER RIGHT button. In this video, I evaluate simple expressions and define a function.