Physics.Arcade.Body#setCircle()

Sets this Body as using a circle, of the given radius, for all collision detection instead of a rectangle.
The radius is given in pixels and is the distance from the center of the circle to the edge.

You can also control the x and y offset, which is the position of the Body relative to the top-left of the Sprite.

To change a Body back to being rectangular again call Body.setSize.

Note: Circular collision only happens with other Arcade Physics bodies, it does not
work against tile maps, where rectangular collision is the only method supported.