CSS Shapes can be defined using the Asic-shape> type. In this guide, we discuss creating rectangles, circles, ellipses, and polygons with the shape-outside property. These are features defined in the CSS shapes module....CSS Shapes can be defined using the <basic-shape> type. In this guide, we discuss creating rectangles, circles, ellipses, and polygons with the shape-outside property. These are features defined in the CSS shapes module.