Superellipse Shapes
The new “Superellipse shapes” is a curve that lies between the ellipse and the rectangle. This is an extremely unique and outstanding shape. In Flutter, a package helps you make superellipse shapes.

To make it, follow the steps below:
class SuperellipseDemo extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Material(
color: Colors.blueAccent[400],
shape: SuperellipseShape(25.0),
child: Container(
width: 100.0,
height: 100.0,
), // Container
); // Material
}
}
GitHub
https://github.com/Salby/superellipse_shape