:root{
  --hauteur-menu: 35px;
}

* {
  margin: 0px;
  padding: 0px;
  font-family: Montserrat, sans-serif;
}

nav {
  width: 100%;
  font-size: 10px;
  position: sticky;
  
  top: 0;
}

nav > ul {
  display: flex;
  text-align: center;
  box-shadow: 0px 1px 2px 1px rgba(0,0,0,0.3);
  height: var(--hauteur-menu);
}

nav ul {
  list-style-type: none;
}

nav > ul > li {
  background-color: #DAF7A6;
  position: relative;
  height: 100%;
  flex: 1;
  
}

nav > ul > li:hover > a{
  color: white;
}

nav > ul > li > a {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  padding:0;
}

li a {
  text-decoration: none;
  color: darkgreen;
}

.menu-deroulant > a:after{
  content: '❯';
  font-size: 14px;
  color:red;
  margin-left: 7px;
  display: inline-block;
}

.menu-deroulant:hover > a:after{
  animation: rotationFleche 0.2s linear forwards;
}

@keyframes rotationFleche {
  0% {
    transform: rotate(0deg);
  }
  50% {
    transform: rotate(45deg);
  }
  100%{
    transform: rotate(90deg);
  }
}

.sous-menu {
  margin-top: var(--hauteur-menu);
  width: 100%;
  text-align: left;
  overflow: hidden;
  max-height: 0;
  border-radius: 2px;
  background-color: white;
  
}

.menu-deroulant:hover > .sous-menu {
  animation: apparitionSousMenu 1s forwards;
}

@keyframes apparitionSousMenu {
  0% {
    box-shadow: 0px 3px 3px 1px rgba(0,0,0,0);
    border-top: 3px solid #2169EC;
  }
  30% {
    box-shadow: 0px 3px 3px 1px rgba(0,0,0,0.3);
  }
  100% {
    max-height: 350em;
    border-top: 3px solid #2169EC;
    box-shadow: 0px 3px 3px 1px rgba(0,0,0,0.3);
    
  }
}

.sous-menu > li:hover {
  background-color: rgba(33, 105, 236, 0.3);
}

.sous-menu > li > a {
  height: 60px;
  padding-left: 5px;
  width: 100%;
  align-items: center;
  display:flex;
}

.sous-menu > li:hover > a {
  color: magenta;
}
div#classe {position: absolute; z-index: 4;}
div#contenu {position: relative; z-index: 3;}