Add a shadow to a color-filled polygon

How to add a shadow to a color-filled polygon.

1. While the filled polygon is selected, tap the second-level menu→Polygon selection→Copy polygon selection
2. Poly select→shadow/gradient
3. Adjust the postion. Lower the shadow, under the color-filled polygon. You can change the color of the shadow (e.g. blue) if you don't like the grey shadow.