This code is an arduino implementation of a 90's electronic toy called Lights Out!. For a 3x3 grid of buttons with integrated LEDs, the goal is to turn all the lights on. The challenge is that on pressing any button to flip from on to off, the four buttons surrounding it also flip their status.
Interesting bits of this code are a series of delays and a simple smoothing algorithm to make the button presses feel responsive without flipping too many times when a button is pressed.
More information about the hardware and general project information at: http://hyperg0at.com/2013/10/whiteout.php
Enjoy!