Stu-Rex ,

If you buy this app you may get good at throwing an excellent curve ball to build a forest but it will not help you to learn how to throw excellent curve balls in another game to compete research tasks. Only a dollar so not a big loss, but my recommendation if you are wanting to learn a better curveball is go to a stop or an area of town with lots of mons and practice on the real thing. I was able to achieve my excellent curveball by throwing a Taurus mons because the circle is much bigger.