Lattice Multiplication

Do you know this method of multiplication? If not, you can see this:

One of the messages says "top left" for all four squares. Otherwise nicely done.

when i first tried, i got stuck because i forgot i had to press space

Fixed that, including the draggable thing.

i dont get it

What do you mean by "I don't get it"?

Did you mean that you don't get the answer or the update?

edit: i just realised i had to press space a few more times