type alias Position = { x : Float, y : Float }
type alias Velocity = { vx : Float, vy : Float }

type alias CircleData = { radius : Float }
type alias RectangleData = { height : Float, width : Float }
type Shape = Circle CircleData | Rectangle RectangleData

type alias Body = { position : Position , shape : Shape , velocity : Velocity }

type alias Rounded a = { a | shape : CircleData }
type alias Boxed a = { a | shape : RectangleData }

type alias Block = Boxed Body
type alias Fireball = Rounded Body

Function `updatePositionByTime` is expecting the 2nd argument to be:
    Body
But it is:
    Rounded Body

updatePositionByTime : Time -> Body -> Body