Can Hackvision display color?No. To produce color in a composite video signal, the microcontroller would need to output a sine wave called the "color burst" at the beginning of each scanline. Since the ATmega328 does not have the ability to output an analog voltage, this isn't possible without an external digital to analog converter (DAC) circuit. The Arduino "analogWrite" function is not actually analog output, but PWM output -- the output of a digital pin on the microcontroller can never be a value between 0V and 5V.
Will Hackvision work on my TV?Almost certainly. Nearly all TVs should be able to handle the composite video signal produced by the TVout library. Hackvision was also tested on a PAL television in the UK (thanks Mowcius!). I have a receiver that refuses to convert the signal to an HDMI output for my home theater projector, but every other TV I've tested on works. If your TV does not work, you may need to add the 75 ohm resistor as described in the troubleshooting section of the build page.
Can I modify the games that come with Hackvision?Yes! The current Hackvision firmware includes a Space Invaders game and a Pong game. If you have the Arduino IDE and a USB to TTL serial cable or adapter like this or this then you can upload your own hacked games to Hackvision.
What kind of other controllers can I add to my Hackvision?Anything you can imagine, really! The unused I/O pins are available for use. Keep in mind that the voltage regulator can supply only 100mA of current, though. The Hackvision itself draws about 25mA, so you've got 75mA of current to work with.
Can I use my own power supply?Yes, if you have a power supply with a center-positive 2.1mm barrel plug it should work. I recommend 9V, but anything between 7V and 12V should work. A 12V supply might cause the voltage regulator to get a little warm. The voltage regulator is rated for 100mA. My testing indicates that under normal conditions the Hackvision draws only about 25mA of current.