Use Path edit tool

Because this is the vector graphic design, so you can edit elements by edit the path point.

1. Double click on an element or click edit button Screenshot 2014-09-26 13.50.39 on left toolbox.
2. Click on the path to add a point. Screenshot 2014-09-28 14.15.53
3. Click on the point and drag to move it, you also can choose multiple point and adjust them together. Screenshot 2014-09-28 14.18.27
4. Double click on the point to switch the point to curve point. Screenshot 2014-09-28 14.19.19
5. Drag the curve adjust point to adjust two point together. And press Command(mac) or Control(windows) key and drag the point to adjust only one side curve. Screenshot 2014-09-28 14.20.57
6. By this way, you can create any special shape that you want. Screenshot 2014-09-28 14.24.13

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