When working with shapes available in PowerPoint, you are not limited to what their default appearance looks like. You can change a rectangle to a rhombus, or even edit a curved or freeform line differently using the Edit Points option available for shapes. This option almost makes PowerPoint almost a drawing program that provides you the option to play with vertexes (points), handles, etc. — very similar to what you would do in Adobe Illustrator.
Here are links to Edit Points tutorials on Indezine – choose a tutorial that explains how to use these options in your version of PowerPoint:
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