This will...only work when the gambeoy itself is looking to read buttons though. If you want to be able to read presses at any time, I cannot help you. To be honest, the gameboy may be looking for a button press a million times a second, so the compromise is minimal at best.

Oh that's quite enough for me Thank you kindly

I suggest connecting P10 - P15 to digital inputs. Enable pull ups on your P10-P13 inputs. Conventional code will
1. activate P14,
2. read P10 - P13
3. deactivate P14
4. activate P15
2. read P10 - P13

Connect P14 and P15 to interrupts and when one goes low, read P10-P13. The datasheet will tell you how to know which button is pressed.

The idea: RGB backlight + RGB LEDs to illuminate silicon buttons. All controlled by Arduino.

When a button pressed it lights up in its own color (say, A - red, B - green, DPAD-blue, etc).

In the variable clock mode (when LTC is on that is) all buttons are lit and the color changes depending on the speed. Blue (Slow) -> Red (Fast). Thus the pot will be a stereo pot.

Now the question is - how to let arduino know that a button was pressed?