Size, Scaling and Fading
You can change the default size of a sprite by setting its 'size' parameter as a multipler of its native size. For example "where size=.5" will make the sprite half size.
'size' applies to both the x and y directions of the sprite.
The sprite parameters 'xscale' and 'yscale' work like size, but only in the direction they indicate.
Fading is done by changing the sprite's 'alpha' value.
"where alpha=0.1" sets the sprite to be almost completely transparent.
"where alpha=1" sets the sprite to be completely opaque.