.menu {
  margin: 0;
}
nav {
  background-color: black;
  border-bottom: 5px solid #37a29b;
  overflow: auto;
}
nav ul {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 20px 10px 0 10px;
}
nav li {
  flex: 1 0 auto;
}
nav li a {
  display: block;
  padding: 10px 20px;
  text-decoration: none;
  text-align: center;
  font-size: 14px;
  color: #ffffff;
}
nav li a:hover {
  background-color: #37a29b;
  border-radius: 10px 10px 0 0;
}
nav > ul > li > ul {
  visibility: hidden;
  opacity: 0;
  z-index: 1;
}
nav > li:hover ul {
  display: block;
  position: absolute;
  padding: 0;
  margin: 0;
  top: 1.5em;
  left: 0;
  list-style-type: none;
  border: 1px solid gray;
}