body, nav.menu, nav.menu label p, .menu ul, .menu li, .menu label, .menu input, .menu a{
  margin: 0;
  padding: 0;
}

nav.menu{
  display: flex;
  position: relative;
}

.menu ul{
  position: relative;
  display: flex;
  flex: 1;
  justify-content: center;
  flex-wrap: wrap;
}

.menu  li{
  display: inline-block;
  flex: 1;
  text-align: center;
  min-width: 180px;
  max-width: 250px;
  line-height: 200%;
  height: 2em;
  border: 1px solid white;
  background-color: black;
}

.menu label, .menu a{
  position: relative;
  display: block;
  font-size: 1em;
  text-decoration: none;
  color: white;
}

.menu label{
  cursor: pointer;
  display: block;
}

.menu label + input{
  display: none; /* hide the checkboxes */
}

.menu ul ul li a, .menu ul ul li label{
  position: relative;
  background: grey;
  color: black;
}

.menu ul ul ul li a, .menu ul ul ul li label{
  position: relative;
  background-color: silver;
  color: black;
}

.menu ul ul{
  position: relative;
  flex-direction: column;
  width: 100%;
  display: none;
}

nav.menu > ul:hover, .menu  li:hover, nav.menu > ul:active, .menu li:active{
  transform: scale(1.05);
  font-weight: bold;
}

.menu label + input:checked + ul{
  display: flex;
}

/*media query*/

@media screen and (max-width: 640px){
  nav.menu > label p{
    position: relative;
    display: inline-block;
    padding: 1.6vh;
    padding-bottom: 2.3vh;
    box-sizing: content-box;
    width: 6.5vh;
    height: 6vh;
    line-height: 1.4vh;
    font-weight: bolder;
    text-align: center;
    background-color: black;
    color: white;
  }

  .menu ul{
    flex-direction: column;
    position: absolute;
    top: 9.9vh;
    left: 0;
    width: 100%;
    display: flex;
    display: none;
  }

  .menu li{
    width: 180px;
    display: block;
    top: 2em;
    left: 0;
  }

  .menu ul ul{
    position: relative;
    top: auto;
  }

  .menu label + input:checked + ul{
    display: flex;
  }