CircularLayout is a special layout that places widgets around a circle.
See the widget's documentation and the example for more information.
size_hint_x is used as an angle-quota hint (widget with higher size_hint_x will be farther from each other, and viceversa), while size_hint_y is used as a widget size hint (widgets with a higher size hint will be bigger).size_hint_x cannot be None.
Widgets are all squares, unless you set size_hint_y to None (in that case you'll be able to specify your own size), and their size is the difference between the outer and the inner circle's radii. To make the widgets bigger you can just decrease inner_radius_hint.