How can I make the menu appear smoothly?

Question

css

There is a simple menu here. How to make that when you click on the first element of the submenu, it slowly "floats" from under it.

Answer 1

.submenu {
  max-height: 0;
  overflow: hidden;
  transition: all 1s ease;
}
.submenu.active {
  max-height: 200px;
}

Use max-height in submenu

Answer 2

use animation and transition