<h3 onclick="document.getElementsByTagName('nav')[0].className = 'menu menu_active'">&lt;menu/&gt;</h3>
<nav class="menu">
  <p onclick="document.getElementsByTagName('nav')[0].className = 'menu'">&lt;close/&gt;</p>
  <ol>
    <li class="menu-item"><a href="#0">Home</a></li>
    <li class="menu-item"><a href="#0">About</a></li>
    <li class="menu-item">
      <a href="#0">Widgets</a>
      <ol class="sub-menu">
        <li class="menu-item"><a href="#0">Big Widgets</a></li>
        <li class="menu-item"><a href="#0">Bigger Widgets</a></li>
        <li class="menu-item"><a href="#0">Huge Widgets</a></li>
      </ol>
    </li>
    <li class="menu-item">
      <a href="#0">Kabobs</a>
      <ol class="sub-menu">
        <li class="menu-item"><a href="#0">Shishkabobs</a></li>
        <li class="menu-item"><a href="#0">BBQ kabobs</a></li>
        <li class="menu-item"><a href="#0">Summer kabobs</a></li>
      </ol>
    </li>
    <li class="menu-item"><a href="#0">Contact</a></li>
  </ol>
</nav>

$grey: #4d4d4c;
$yellow: #efc371;
$purple: #ae94c0;
$green: #b5bc67;
$orange: #dd925f;

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    position: relative;
    font-weight: 400;
    list-style-type: none;
    font-style: normal;
}

body {
    background: linear-gradient(to right, #c04848, #480048);
    height: 100vh;
}

a {
    color: inherit;
    text-decoration: none;
}

nav {
    line-height: 1.4;
    font-family: "Space Mono", monospace;
    background: #1d1f20;
    padding: 25px 35px;
    width: 300px;
    top: calc(50vh - 247px);
    left: calc(50vw - 150px);
    position: fixed;
    border-radius: 16px;
    box-shadow: 0 0 60px -15px black;
    transform: scale(0) rotate(360deg);
    transition: all 0.75s;
    font-size: 18px
}

nav.menu_active {
    transform: scale(1) rotate(0deg);
}

nav > ol > li {
    margin: 20px 0;
    color: $green;
}

nav > ol > li:first-of-type {
    color: $yellow;
}

nav > ol > li > ol {
    margin: 10px 0 0 20px;
    border-left: 1px solid $grey;
    color: $purple;
}

nav > ol > li > ol > li {
    margin: 7px 0;
    padding-left: 20px;
}

nav a:hover {
    color: $orange;
}

h3 {
    position: fixed;
    font-family: "Roboto Mono", monospace;
    font-size: 60px;
    color: #cfd8dc;
    top: calc(50vh - 40px);
    left: calc(50vw - 126px);
    cursor: pointer;
    transition: all 0.3s;
}

h3:hover {
    border-bottom: 6px dotted #cfd8dc;
    padding-bottom: 10px;
    top: calc(50vh - 50px);
}
 
p {
    font-family: "Roboto Mono", monospace;
    float: right;
    cursor: pointer;
    font-size: 16px;
    color: #cfd8dc;
    transition: all 0.2s;
}

p:hover {
    border-bottom: 2px dotted #cfd8dc;
    padding-bottom: 5px
}