click or drag to draw shape, double click to close
drag to shift hue, scroll to shift value
drag to move, right drag to scale and rotate, double click or scroll to change z-order
tap or drag to draw shape, double tap to close
tap to select, drag to shift hue, two finger scroll to shift value
tap to select, one finger to move, two fingers to scale and rotate,
double tap or three finger drag to change z-order