press 1, 2 or 3 to change platform click to create a ball press space to fire a ball in the direction of the mouse from the centre of the screen press d to delete all balls If you wan't to make your own slope you can click see inside and use the add platform function.
thanks to Java_Programmer If you are interested you may also like my other physics program: https://scratch.mit.edu/projects/251695315/#player And here are some more of my projects: https://scratch.mit.edu/studios/5242825/