If asked, most children would said they play video games for the first time in their life as a game of hitting the ball to the wall. Making bouncing ball is very easy to do in Scratch. I would teach you step on how to make it, step by step.
First, we have to make a new Sprite for a ball. The ball will always bounce back when hitting the wall to the appropriate direction. It's easy to draw the costume for a ball.
Now it's time to make a new Script for your Ball Sprites. Remember that we have to start play our games when the Green Flag being clicked. So we have to use this block to control our games. Don't forget to set the coordinate of the ball every time we play the games so that the ball never loss to the outside of the Stage. Now I will show you, that Scratch have very nice block that can do our job automatically. Look at the Motion Blocks Palette and you will see the block "if on edge, bounce". This is very useful block and you can use it for many kind activity in usual games. Finally you must use that blocks within forever block, so that Scratch will evaluate this block, as long as we don't click Stop button. But it's not enough. What the ball will do after it bounces? They have move some steps away from initial position without ending. So we have our conclusion right now. The complete blocks, or we call stack, for our ball sprite is the combination of all the blocks I have described. Now you can build your own bouncing ball games. For the next time, I will show you how to complete this game with racket for hitting the ball. Bye.