func (gn *Engine) throwOneBall(b *model.Ball, direction model.Direction) {
// Before throwing, normalize the Y coordinate to a dimensionless
// percentage. Recipient converts it based on their own dimensions,
// so that if the ball left one tenth of the way up the screen, it
// enters the next screen at the same relative position.
b.SetPos(b.GetPos().X, b.GetPos().Y/gn.scn.Height())
gn.chBallCommand <- model.BallCommand{b, direction}
}
