Press the green flag. Then press space. (I haven't finished with the start scene yet. Sorry.) Move the green "paddle" around. When the cat touches the paddle, you score a point. When the cat touches the red area, you lose points. The game never ends, unless you press the red stop button.
This is really a draft because the open scene isn't done. However, the rest is done. Press space to start playing until I finish. I made this using Scratch help during Hour of Code week in 2014. I made it before I searched for and saw other 'cat-pong's out there. It is original, and my first game. Also, post your high score in the comments below. 1.0.1: The cat shouldn't get stuck now. Thanks @mathematicskid! Aug. 28, 2015: @MabonBalavedaKain has fixed it so that the cat goes in a random direction each time. We now no longer need @mathematicskid's fix, but she helped SO MUCH! 1.0.2: Thanks to @MabonBaladevaKain, the cat now goes in random directions! However, this does mean that the cat can go through the paddle. I guess you're just going to have to try to catch the cat before it hits the red... ; ) For more info please visit the studio: https://scratch.mit.edu/studios/1084982/