f32/d2/rect.go
func RectFromCircle(c Vec2, r float32) Rectangle {
	return RectWH(c[0]-r, c[1]-r, 2*r, 2*r)
}
func RectFromCircle(c Vec2, r float32) Rectangle {
	return RectWH(c[0]-r, c[1]-r, 2*r, 2*r)
}
// RectFromCircle returns the minimum rectangle that contains the circle of
// center c and radius r