Syntax @_GRADDIRECTION{TB|BT|LR|RL}
Description Allows you to specify the direction of the background gradient. You should specify your preference at the end of the command. The available settings are: TB (top-to-bottom), BT (bottom-to-top), LR (left-to-right), and RL (right-to-left).
These settings specify movement from the background color to the gradient color. For example, if you set this to TB (top-to-bottom), the top of the background will be painted in the background color, while the bottom will be painted in the gradient color.
This command will have no effect if a gradient color has not been specified in the appearance file or with the @_GRADCOLOR command.