If you are only twelve and you already have a basic understanding of Blender(others often find its UI very hard) and python then you will go far. Remember to invest a little time each day and you will always be improving.
Don’t be afraid to scale up a bit after you’ve done couple of basic games like this, you seem to handle things pretty good. If you do some modeling and texturing you can make your games have themes and settings which make things more interesting to watch as you play.