A flying element behind the cursor - how to prevent flying outside the parent?

Question

JavaScript

Hello!

Here, I found about what I need (Example # 1)


How to make it so that if I move the cursor away from the square (parent), then the element remains visible inside the parent .. that is, it remains at the edge of the block from which the cursor left?

+ now this element interferes with the cursor (for example, if you try to select text)..