Scratch is not a real great game platform. Although you can learn some very basic fundamentals I would suggest you look to learning a language or if you want to go straight to a game platform go do the Unity beginners tutorials. Scratch looks just like ALICE (google alice programming language) and you can find a lot more info on games made with ALICE From what I see they are identical but I havent used scratch. I used ALICE to teach my daughter to program but even she is in python now and she is ten.
I do not want to stop you from doing what you want. By all means go and play with scratch but I think it will only frustrate someone who wants to build anytype of game be it even a simple sidescroller.
This is only one opinion ask lots of people and then make up your mind. (Learn c++, or any of the C derivatives such as D or C# etc or python)