Code Sketch

cleari()
drawStage(ColorMaker.white)

def pic = Picture.circle(25)
    .thatsFilledWith(cm.radialGradient(10, 10, white, 25, red, false))
    .thatsStrokeColored(noColor)

var velocity = Vector2D(8, 8)

case class Bouncing(velocity:Vector2D, shape:Picture){
    

    def handle:Bouncing = {
        def movedShape = 
            shape
            .thatsTranslated(velocity.x, velocity.y)
        return handleBounce(movedShape)
    }

    def handleBounce(shape:Picture):Bouncing = {
        shape.draw()        
        
        def shapeCollideWithBorder = shape.collidesWith(stageBorder)
        
        return if (shapeCollideWithBorder){
            Bouncing(
                bouncePicVectorOffStage(shape, velocity),
                shape.copy
            )      
        } else {
            Bouncing(
                velocity,
                shape.copy
            )             
        } 
    }

    
}

animateWithState(Bouncing(velocity, pic)) { s =>
    erasePictures()
    s.handle
}