Fixed Left Menu scrolling not working? - css

Question

I have made following demo on Codepen. Problem is when the height of viewport is decreased scroll appear which i want but logo is hidden under icon-list which is the unwanted behavior. Everything works properly if viewport height is enough.
<input type="checkbox" id="menu-expander" name="ert">
<div class="main-menu-container">
<div class="logo-area">
<div class="logo"><img src="http://extensiondl.maxthon.com/skinpack/11018970/1375652328/icons/icon_32.png"></div>
</div>
<ul class="sidebar-icon-list">
<li class="sidebar-icon">
<img src="http://www.clipartsfree.net/vector/small/go-home_Clipart_Free.png">
<span>Week</span>
</li>
<li class="sidebar-icon menu-active">
<img src="http://www.clipartsfree.net/vector/small/go-home_Clipart_Free.png">
<span>Projects</span>
</li>
<li class="sidebar-icon" title="Life">
<img src="http://www.clipartsfree.net/vector/small/go-home_Clipart_Free.png">
<span>Life</span>
</li>
<li class="sidebar-icon">
<img src="http://www.clipartsfree.net/vector/small/go-home_Clipart_Free.png">
<span>Analysis</span>
</li>
<li class="sidebar-icon">
<img src="http://www.clipartsfree.net/vector/small/go-home_Clipart_Free.png">
<span>Projects</span>
</li>
</ul>
<div class="sidebar-wt">
<label for="menu-expander"><img src="https://cdn3.iconfinder.com/data/icons/awesome-lineca-vol-1/17/angle-right-128.png"></label>
</div>
<div class="user-area">
<div class="user-pic"></div>
</div>
CSS
input[name="ert"] {
position: absolute;
opacity: 0;
width: 0;
height: 0;
overflow: hidden;
}
/* Main Menu Contaier */
.main-menu-container {
width: 6em;
position: fixed;
top: 0;
left: 0;
height: 100vh;
background-color: hsl(207,6%,12%);
color: #fff;
display: flex;
flex-direction: column;
z-index: 100;
border-right: 1px solid black;
transition: width 0.2s ease-in;
overflow-y: auto;
overflow-x: hidden;
}
input[name="ert"]:checked + .main-menu-container {
width: 12em;
transition: width .3s linear;
}
/* Logo Area */
.logo-area {
height: 6em;
background-color: #fff;
display: flex;
flex-direction: column;
align-items: center;
justify-content: center;
}
.logo {
height: 4em;
width: 4em;
}
.logo img {
height: 4em;
width: 4em;
}
/* Icon List */
.sidebar-icon-list {
display: flex column;
list-style: none;
width: 100%;
padding: 0;
margin: 0;
flex-grow: 1;
}
.sidebar-icon {
color: #eaeaea;
width: 100%;
border-left: 3px solid hsl(207,6%,12%);
height: 3em;
margin: 1em 0;
display: flex;
flex-direction: column;
justify-content: center;
align-items: center;
cursor: pointer;
position: relative;
transition: all 0.3s linear;
}
.sidebar-icon:hover {
color: #fff;
border-left: 3px solid #EEFF22;
}
.sidebar-icon img {
color: #fff;
width: 2em;
height: 2em;
}
.sidebar-icon span {
font-size: 0.75em;
opacity: 0;
position: absolute;
transition: all 0.1s linear;
}
input[name="ert"]:checked + .main-menu-container .sidebar-icon-list .sidebar-icon {
flex-direction: row;
justify-content: flex-start;
padding-left: 1em;
transition: all 0.3s linear;
}
input[name="ert"]:checked + .main-menu-container .sidebar-icon-list .sidebar-icon span {
font-size: 0.75em;
opacity: 1;
position: relative;
transition: all 0.3s linear;
margin-left: 1em;
}
.menu-active {
border-left: 3px solid #EEFF22;
color: #EEFF22;
}
/* Sidebar Expander */
.sidebar-wt {
display: flex;
justify-content: flex-end;
}
.sidebar-wt label img {
height: 1.5em;
width: 1.5em;
cursor: pointer;
}
.main-menu-container .sidebar-wt label img {
transition: all 0.3s linear;
}
input[name="ert"]:checked + .main-menu-container .sidebar-wt label img {
transform: rotateZ(180deg);
transition: all 0.3s linear;
}
/* USer Area at Bottom */
.user-area {
height: 4em;
background: #fff;
display: flex;
align-items: center;
justify-content: center;
}
.user-pic {
width: 100%;
height: 5em;
border-bottom: 2px solid #2ca58d;
background-image: url(http://soccer1x2.net/wp-content/uploads/2012/03/leo-messi1.png);
background-size: cover;
}
.main-menu-container .sidebar-wt label img {
transition: all 0.3s linear;
}
input[name="ert"]:checked + .main-menu-container .sidebar-wt label img {
transform: rotateZ(180deg);
transition: all 0.3s linear;
}

Answer 1

It looks like the height of .logo-container is changing, when you decrease the window's height.
If you min-height: 6em; for .logo-area the height will not decrease.