First off, just wanted to show you that it doesn't actually have to be static. Any image will do, though obviously, images with large contrasting bits (like the purple background and dark tiles) causes greater visual ambiguity. However, if the texture of the text in this image were moving too (in a different direction from the background, obviously), it would likely look fine.

Though there's nothing stopping someone from taking a picture of their dog and going with it, I think the effect really does work best with sort of flat repeating textures like the purple background. It doesn't have to be static and might in fact be easier on the eyes than static.

Gradients have a very interesting property. They are directional. This means that if the direction of the background gradient is moving down, then the result is something like a fading in effect. However, if it is going side to side, the gradient will not change and the text will remain invisible. So, if you could control the direction of the background, moving it one way would make text invisible, while moving it another will cause the text to show.

I was thinking how one might use this on an iPod Touch / iPhone to make a game. The Touch has some unique properties that can be used to great effect. The first is the accelerometer - a little device in the Touch which tells you which direction it is tilting. The obvious springs to mind: labyrinth! Or Kirby's Tilt n' Tumble if you had a digitally blessed childhood. Basically, you control a ball by tilting the Touch, trying to avoid touching the walls. Go from one end of the maze to the other and escape. Simple really. Obvious even. If there isn't already a labyrinth game on the iPod Touch as of writing this, somebody is neglect in their duties.

Okay, how is the White Noise concept used in an interesting manner? Well, the background is moving in one direction (shown here with a little motion blur going up and down), and this motion will contrast against other motion (like the wall obstacle here, with the motion going left to right).

Using the touch pad and a flick gesture, one can set the direction and speed of the background texture. You'll notice that the obstructing wall is now invisible - so you can roll right on through it.. Long story short, by moving the background matching another, you essentially make it part of the background.

How can this be used? Take an enemy which has a heart that you can bump into to do damage (we'll even throw in a splash of color and make it red static). Unfortunately it's surrounded by a shell of static going in a particular direction. Flick the static to match the shell, the shell will effectively disappear and you can bump the heart without problem.

You can also use it to match the static on your ball. By stopping the static, your ball will become indistinguishable from the background - perhaps causing enemy shots to go right through you. Or maybe there is a boss that likes to blend into the background, and you have to constantly move the static around to find him. Perhaps you come into an empty room and as far as you can tell, there's no way out. Flick the static in a new direction to reveal a hidden exit.

Maybe the early levels use statics and simple textures, but later levels make it more difficult. For instance, one level could use gradients, where the directional texture will open up new puzzle opportunities. Or an image can be used, like above, where one must shift the image around and match it to the foreground to reveal hidden messages.

There's really a lot of possibilities here. In fact, I've already got an idea for White Noise 3 that using a touch screen in a completely different way.