A rectangle that does the opposite of the mouse's movements using unidirectional data flow. When you click, it brings the rectangle back to the mouse.

What I used for help/inspiration:

To change to rectangle: https://developer.mozilla.org/en-US/docs/Web/SVG/Element/rect

To change color of rectangle: https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/style