Animation not working correctly in ul?

Question

css

There is a menu on ul with several items inside.
Initially, ul has zero height and the specified transition (all .3s ease).
When changing the height of the ul, the animation does not work. That is, the height of the list from zero to normal changes instantly. But when the list height is reduced back to zero, the animation works.
What could be the problem? Will suit any solution, even the most crutch of crutches.

Answer 1

Perhaps you have the transition parameter set to hover (on hover). If so, put it initially for ul in this form

<ul>
<li>...</li>
<li>...</li>
</ul>
ul {
height:...;
transition: 0.3s;
}