Webleb - fragmentos de código - Barra de navegación HTML con menú desplegable y estilo

<body>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href='https://fonts.googleapis.com/css?family=Ubuntu Sans' rel='stylesheet'>
<style>
p {
  font-size:30;
  color: white;
  font-family: Ubuntu Sans;
  position: absolute;
  top: 16%;
  left: 3%;
  right: 40%; 
  
}
p{text-align: left;}

body{
  background-image: linear-gradient(rgba(0, 0, 0, 0), rgba(0, 0, 0, 0)), url('https://photojournal.jpl.nasa.gov/jpeg/PIA24466.jpg');
  background-repeat: no repeat;
  background-attachment: fixed;  
  background-size: cover;
}
ul {
  list-style-type: none;
  padding: 0;
  margin:0px;
  overflow: hidden;
  background-color: black;
  font-family: Ubuntu Sans;
  position: fixed;
  top: 0;
  width: 100%

}
li {
  float: left;
}

li a {
  display: block;
  color: white;
  text-align: center;
  padding: 16px 18px;
  text-decoration: none;
  font-size: 15px;
}
li a:hover:not(.active) {
  background-color: #333;
  border-radius: 100px;
}
.active {
  background-color: black;
}
.dropdown {
  display: inline-block;
  position: absolute;
  top: 8px;
  right: 16px;  
}
.dropdown-content {
  display: none;
  position: 800% 300%;
  background-color: #f9f9f9;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
  padding: 50px 50px;
  z-index: 1;
  border-radius: 20px;
  overflow-x: hidden;
  overflow-y: scroll;
  scroll-snap-type: y mandatory;
}
.dropdown:hover .dropdown-content {
  display: block;
  cursor:help;
}
#Drop{color:Tomato;}
#Drop:hover{cursor:help;}
#Drop{font-size: 20px;}
#Drop{font-family: Ubuntu Sans;}
#vocab{width: 90px;}
</style>
<body>
<ul>
  <li><a class="" href="Ingenuity on mars.html">Home</a></li>
  <li><a href="How does Ingenuity work.html">How does it work?</a></li>
  <li><a href="Limit.html">Limiting engineering factors</a></li>
  <li><a href="why.html">Why?</a></li>
  <li><a href="Next.html">Whats Next?</a></li>
</ul>
    <div class="dropdown">
  <span id = "Drop">Vocabulary ⯆</span>
  <div class="dropdown-content">
  <ol id = "vocab">
  <li>...</li>
  <li>...</li>
  <li>...</li>
  <li>...</li>
  <li>...</li>
  </ol>
  </div>
</div>
</body>

Validating your code, please wait...

HTML

CSS

}
li {
  float: left;
}