Every background is composed of 2 layers/images.
To create the distortion effect, the following function is used:
```Offset (y, t) = A sin ( F*y + S*t )```
where:
y is the vertical coordinate being transformed
t is time that's elapsed
A is the amplitude
F is the frequency
S is the speed or frameskip of the transformation
Offest refers to the y direction of the shift at a given time t.
There are also three types of distortions that use the result of the Offset function:
Horizontal translations, where each line is shifted left by the given number of pixels
Horizontal interlaced translations, where every other line is shifted right by the given number of pixels
Vertical compression translations, where each line is shifted up or down by the given number of pixels