Move the paddle/green line a when the ball comes hit it before it touches the floor/red line. If it does, click the green flag and start over. The score changes by five points every time you hit the ball, I’m on an iPad so I’m not exactly sure if you can use the mouse or whatever, but if your on a iPad click on the screen.
I did a tutorial to make this called pong game. If you want to make it just watch it. SPECIAL THANKS TO MY TECH TEACHER!