Dropdown menu is not showing when I hover over "Planets" menu? - html

Question

I am new to HTML and CSS and was trying to make a random website about astronomy. And I can't figure out what my dropdown menu is not working. I googled a lot and saw many youtube videos, but still cannot find a solution. When I change the display in sub-menu in CSS to block, it shows the submenus but in a horizondal line. Should I rewrite the whole code or is it editable? I am new HTML and CSS so excuse my mistakes and lack of knowledge. Thanks.
*{
margin: 0;
padding: 0;
font-family: Century Gothic;
}
header{
background-image: linear-gradient(rgba(0,0,0,0.5),rgba(0,0,0,0.5)), url(../1.jpg);
height: 100vh;
background-size: cover;
background-position: center;
}
ul{
float: right;
list-style-type: none;
margin-top: 20px;
}
ul li{
display: inline-block;
}
ul li.active a{
background-color: #fff;
color: #000;
}
ul li a{
text-decoration: none;
color: #fff;
padding: 5px 20px;
border: 1px solid transparent;
transition: 0.6s ease;
}
ul li a:hover{
background-color: #fff;
color: #000;
}
.main{
max-width: 1200px;
margin: auto;
}
.title{
position: absolute;
top: 1%;
left: 1%;
}
.title h1{
font-size: 40px;
color: white;
}
.sub-menu{
display: none;
position: relative;
}
.rocks:hover .sub-menu{
display: block;
position: absolute;
margin: 10px;
}
<header>
<div class="main">
<ul>
<li class="active">Home</li>
<li class="rocks">Planets</li>
<ul class="sub-menu">
<li>Mercury</li>
<li>Venus</li>
<li>Earth</li>
<li>Mars</li>
<li>Jupiter</li>
<li>Saturn</li>
<li>Uranus</li>
<li>Neptune</li>
</ul>
<li>Major Moons</li>
<li>About</li>
<li>Contact</li>
</ul>
</div>
<div class="title">
<h1>ASTRONOMY</h1>
</div>
</header>

Answer 1

It's because you have to place your submenu inside the parent <li>.
Here's a working live Codepen.
*{
margin: 0;
padding: 0;
font-family: Century Gothic;
}
header{
background-image: linear-gradient(rgba(0,0,0,0.5),rgba(0,0,0,0.5)), url(../1.jpg);
height: 100vh;
background-size: cover;
background-position: center;
}
ul{
float: right;
list-style-type: none;
margin-top: 20px;
}
ul li{
display: inline-block;
}
ul li.active a{
background-color: #fff;
color: #000;
}
ul li a{
text-decoration: none;
color: #fff;
padding: 5px 20px;
border: 1px solid transparent;
transition: 0.6s ease;
}
ul li a:hover{
background-color: #fff;
color: #000;
}
.main{
max-width: 1200px;
margin: auto;
}
.title{
position: absolute;
top: 1%;
left: 1%;
}
.title h1{
font-size: 40px;
color: white;
}
.sub-menu{
display: none;
position: relative;
}
.rocks:hover .sub-menu{
display: block;
position: absolute;
margin: 10px;
}
<header>
<div class="main">
<ul>
<li class="active">Home</li>
<li class="rocks">Planets
<ul class="sub-menu">
<li>Mercury</li>
<li>Venus</li>
<li>Earth</li>
<li>Mars</li>
<li>Jupiter</li>
<li>Saturn</li>
<li>Uranus</li>
<li>Neptune</li>
</ul>
</li>
<li>Major Moons</li>
<li>About</li>
<li>Contact</li>
</ul>
</div>
<div class="title">
<h1>ASTRONOMY</h1>
</div>
</header>
Let me know in the comment if you need a help styling the dropdown menu.