JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <a href="#" class="menu-button">Меню</a>
  <div class="menu">
    Меню Меню меню
  </div>
</div>

CSS

.menu-button { 
    display:block;
    text-align:center;
    line-height:30px;
    width:50px;
    height:30px;
    background:#CCC;
    text-decoration:none;
}

.menu {
  position: absolute;
  top: 50px;
  left: -400px;
  transition-duration: 0.3s;
}

.container { float:left }

.container:hover .menu {
  left: 0;
}