Flipping a layer
It may sometimes be useful to flip a single layer as opposed to the whole canvas. Pixen provides a simple method for flipping a layer vertically or horizontally.
To rotate a layer:
Right-click (or control-click) the layer you'd like to flip and choose the direction from the Transform Layer submenu
or
Select the layer you'd like to flip in the layers drawer and use the commands in the Layers > Flip Layer menu.