I am working on a OS, and I wanna know how can I do those selection rectangles that appear when you hold the mouse button on the desktop. You hold and drag and a rectangle appears that selects things. Is there any way I can do that? Thanks.

https://scratch.mit.edu/projects/144901273/ is something I did a while ago. You'd have to work out what was inside it though.

Thanks, I did figure out what was inside, I might do that in the future