Can the Gameduino 2 work with the Mega2560?

Yes, but because the Mega2560 has its SPI pins in a different place, you need to make 3 wire hookups. Connect:

You can do this with jumpers. For my Mega2560 I eventually soldered these three wires directly to the pins underneath the Mega.

Can the Gameduino 2 work with the Leonardo or Arduino Yun?

Yes, but because these Arduinos have their SPI signals in a different place, you need to jumper three signals

There is also a shield available that rewires the pins: https://www.sparkfun.com/products/11469

How do I recalibrate the touchscreen?

To force a calibration re-run, load the selftest sketch under 4.Utilities.

The first time the Gameduino 2 boots, it calibrates the touchscreen - asking you to "please tap on the dot" in three places on the screen. It then stores this calibration in Arduino EEPROM.

Is there a way to improve touch-screen performance?

Yes the touch screen is not as responsive as an expensive capacitive screen on a smart-phone. One trick is to use gentle pressure with a fingernail instead of a fingertip. Another is to use a non-metallic stylus. The 3.Peripherals -> sketch app is good for evaluating touch performance.

How can I load a JPEG and use my assets at the same time?

Yes, see this thread for details. http://gameduino2.proboards.com/thread/237/jpgs-assets

Can I dim the screen?

Yes, see this thread: http://gameduino2.proboards.com/thread/46/switch-off-display

How do I display incoming bitmap data on the screen?

See this thread: http://gameduino2.proboards.com/thread/243/display-array-uncompressed-bitmap-data

and http://gameduino2.proboards.com/thread/209/greyscale-bitmap-import-array

How can you display a ``string`` type?

See this thread: http://gameduino2.proboards.com/thread/193/solved-put-string-type-variable