First, you make up some names and give each name a number.
Then you draw shapes based on the names, not the numbers.
For example, you might make a number called my_cool_number, and set it to 10, and then say "draw a circle my_cool_number pixels from the top, and 300 pixels from the left.".
Then your screen shows a circle 10 pixels from the top and 300 pixels from the left.
If I go and drag the circle, g9 will figure out how to change your numbers. For example, if I drag it down, g9 might say "now my_cool_number is set to 100". If my_cool_number is 100, then "draw a circle my_cool_number pixels from the top, and 300 pixels from the left" will draw a circle that's lower down.
That way it's like I'm actually moving the circle.
The cool part is that if you had other parts of your drawing that also depended on my_cool_number, they'll also move when it changes.
For example, you might make a number called my_cool_number, and set it to 10, and then say "draw a circle my_cool_number pixels from the top, and 300 pixels from the left.".
Then your screen shows a circle 10 pixels from the top and 300 pixels from the left.
If I go and drag the circle, g9 will figure out how to change your numbers. For example, if I drag it down, g9 might say "now my_cool_number is set to 100". If my_cool_number is 100, then "draw a circle my_cool_number pixels from the top, and 300 pixels from the left" will draw a circle that's lower down.
That way it's like I'm actually moving the circle.
The cool part is that if you had other parts of your drawing that also depended on my_cool_number, they'll also move when it changes.