It's a Befunge interpreter!
START: switch between EDIT mode and RUN mode
D-pad: move cursor
Keyboard: enter character at cursor position
R-button: Fast mode (no VSYNC)
Your code can only be 32 by 21, because of the screen size.
There can only be about 512 numbers in the stack, and I have also limited the size of numbers.
There is a new instruction: ¥, which acts like & and ~, except it gets button input.
Here are the QR codes: