Change the shape of an element

To change the shape of a line or polygon:

1. Select the element
2. Zoom in to the element you want to work on
3. Select the Change Shape Mode [a] (the number of points on the line will change and the points (called anchors) will now be selectable)
4. Select a single anchor and drag it into position
5. Use the points (called handles) coming out from the selected anchor to modify the shape in more detail

(When exiting Change Shape Mode, the new shape may look a little rough/edgy, but this is handled in all drawing by automated smoothing)

This video shows how:

Remember to save your work.