How to animate mouse in/out action?

Hi,

I’m so beginner with using Velo and some coding. So it could be very basic. But I want to add an animation to my mouse in & out actions, like in this side menu lines. https://neuralink.com/


Actually exactly like this.

I made the same menu, add the lines with mouse events. What code should I use now for the lines have the same animations?

Thank you!