def distance(self, clr):
coord = lambda a, d: (cos(radians(a)) * d, sin(radians(a)) * d)<EOL>x0, y0 = coord(self.h * <NUM_LIT>, self.s)<EOL>x1, y1 = coord(clr.h * <NUM_LIT>, clr.s)<EOL>z0 = self.brightness<EOL>z1 = clr.brightness<EOL>d = sqrt((x1 - x0) ** <NUM_LIT:2> + (y1 - y0) ** <NUM_LIT:2> + (z1 - z0) ** <NUM_LIT:2>)<EOL>return d<EOL>
Returns the Euclidean distance between two colors (0.0-1.0).

Consider colors arranged on the color wheel:
- hue is the angle of a color along the center
- saturation is the distance of a color from the center
- brightness is the elevation of a color from the center
  (i.e. we're on color a sphere)