The gradientmap theme produces an animation of concentric greyscale circles,
suitable for use with the Displace effect to
create a ripple or rain filter.
The 'rain' map also supports 'instances', 'size' and 'stickiness' attributes to control
the number of raindrops, their dimensions and the duration of each ripple.
backcolor: six character hex color value
editable: comma delimited list of property names
forecolor: six character hex color value
id: single word string identifier, starting with a letter
map: rain, ripple, fisheye
length: floating point number (frames)
symbol: a valid SWF URL, followed by an ampersand and class name
type: the string 'theme'