This is the Reference of the Gamebuino Meta. If you have an older Gamebuino, head to the Legacy Reference.
You can download the PDF version
BUTTON_A BUTTON_B BUTTON_MENU (used to be BUTTON_C) BUTTON_UP BUTTON_RIGHT BUTTON_DOWN BUTTON_LEFT
All these function should not be used as they are internal and might change with no backward compatibility. Use at your own risk.