is the title navigation to keep the original position, the bottom border (or the underscore below or the bar floating up). The latter is probably thought of as adding a div fill color at the bottom and then floating it up. I don"t know if the other bosses have a good plan.
this brings me to the idea that borders can be implemented in several ways.
generally, I will use pseudo elements, locate at the bottom, adjust the mouse hover position up, and add a bit of transition
.it is also possible to use a linear gradient, with the bottom frame changing from white to red