Move the mouse side to side to guide where the boxes will fall. Click the green flag to reset and erase the boxes.
The falling box is a clone. When the clone reaches the bottom, it stamps and then deletes itself. This prevents too many sprites from being onscreen at once. The mouse tracker is a separate sprite. Part of my Generative Art for Scratch 3.0 project: https://scratch.mit.edu/studios/32415566