Vertical centering with flexbox [duplicate] - html

Question

This question already has an answer here:
Vertically align a flexbox
(1 answer)
Closed 5 years ago.
I'm currently having issues vertically centering the wrapper. I attempted to create a div that displays flex and aligns items center as suggested by another post and it didn't work. Any ideas why and how to resolve it?
body {
font-family: Arial, sans-serif;
background: #ddd;
}
h1 {
text-align: center;
font-family: "Trebuchet MS", Tahoma, Arial, sans-serif;
color: #333;
text-shadow: 0 1px 0 #fff;
margin: 50px 0;
}
#center {
display: flex;
align-items: center;
}
#wrapper {
width: 100px;
margin: 0 auto;
background: #fff;
padding: 20px;
border: 10px solid #aaa;
border-radius: 15px;
background-clip: padding-box;
text-align: center;
}
.button {
font-family: Helvetica, Arial, sans-serif;
font-size: 13px;
padding: 5px 10px;
border: 1px solid #aaa;
background-color: #eee;
background-image: linear-gradient(top, #fff, #f0f0f0);
border-radius: 2px;
box-shadow: 0 1px 3px rgba(0, 0, 0, 0.15);
color: #666;
text-decoration: none;
text-shadow: 0 1px 0 #fff;
cursor: pointer;
transition: all 0.2s ease-out;
}
.button:hover {
border-color: #999;
box-shadow: 0 1px 3px rgba(0, 0, 0, 0.25);
}
.button:active {
box-shadow: 0 1px 3px rgba(0, 0, 0, 0.25) inset;
}
.overlay {
position: absolute;
top: 0;
bottom: 0;
left: 0;
right: 0;
background: rgba(0, 0, 0, 0.5);
transition: opacity 200ms;
visibility: hidden;
opacity: 0;
}
.overlay.light {
background: rgba(255, 255, 255, 0.5);
}
.overlay .cancel {
position: absolute;
width: 100%;
height: 100%;
cursor: default;
}
.overlay:target {
visibility: visible;
opacity: 1;
}
.popup {
margin: 75px auto;
padding: 20px;
background: #fff;
border: 1px solid #666;
width: 300px;
box-shadow: 0 0 50px rgba(0, 0, 0, 0.5);
position: relative;
}
.light .popup {
border-color: #aaa;
box-shadow: 0 2px 10px rgba(0, 0, 0, 0.25);
}
.popup h2 {
margin-top: 0;
color: #666;
font-family: "Trebuchet MS", Tahoma, Arial, sans-serif;
}
.popup .close {
position: absolute;
width: 20px;
height: 20px;
top: 20px;
right: 20px;
opacity: 0.8;
transition: all 200ms;
font-size: 24px;
font-weight: bold;
text-decoration: none;
color: #666;
}
.popup .close:hover {
opacity: 1;
}
.popup .content {
max-height: 400px;
overflow: auto;
}
.popup p {
margin: 0 0 1em;
}
.popup p:last-child {
margin: 0;
}
iframe {
border: none;
}
<div id="center">
<div id="wrapper">
<p><a class="button" href="#popup1">Click Me</a></p>
</div>
<div id="popup1" class="overlay">
<div class="popup">
<h2>Drop Day</h2>
<a class="close" href="#">×</a>
<div class="content">
<p>Hello</p>
</div>
</div>
</div>
</div>

Answer 1

Your main wrapper (div#center) must have its height defined:
body {
font-family: Arial, sans-serif;
background: #ddd;
}
h1 {
text-align: center;
font-family: "Trebuchet MS", Tahoma, Arial, sans-serif;
color: #333;
text-shadow: 0 1px 0 #fff;
margin: 50px 0;
}
#center {
display: flex;
align-items: center;
/* or any other height you want */
height: 100vh;
}
#wrapper {
width: 100px;
margin: 0 auto;
background: #fff;
padding: 20px;
border: 10px solid #aaa;
border-radius: 15px;
background-clip: padding-box;
text-align: center;
}
.button {
font-family: Helvetica, Arial, sans-serif;
font-size: 13px;
padding: 5px 10px;
border: 1px solid #aaa;
background-color: #eee;
background-image: linear-gradient(top, #fff, #f0f0f0);
border-radius: 2px;
box-shadow: 0 1px 3px rgba(0, 0, 0, 0.15);
color: #666;
text-decoration: none;
text-shadow: 0 1px 0 #fff;
cursor: pointer;
transition: all 0.2s ease-out;
}
.button:hover {
border-color: #999;
box-shadow: 0 1px 3px rgba(0, 0, 0, 0.25);
}
.button:active {
box-shadow: 0 1px 3px rgba(0, 0, 0, 0.25) inset;
}
.overlay {
position: absolute;
top: 0;
bottom: 0;
left: 0;
right: 0;
background: rgba(0, 0, 0, 0.5);
transition: opacity 200ms;
visibility: hidden;
opacity: 0;
}
.overlay.light {
background: rgba(255, 255, 255, 0.5);
}
.overlay .cancel {
position: absolute;
width: 100%;
height: 100%;
cursor: default;
}
.overlay:target {
visibility: visible;
opacity: 1;
}
.popup {
margin: 75px auto;
padding: 20px;
background: #fff;
border: 1px solid #666;
width: 300px;
box-shadow: 0 0 50px rgba(0, 0, 0, 0.5);
position: relative;
}
.light .popup {
border-color: #aaa;
box-shadow: 0 2px 10px rgba(0, 0, 0, 0.25);
}
.popup h2 {
margin-top: 0;
color: #666;
font-family: "Trebuchet MS", Tahoma, Arial, sans-serif;
}
.popup .close {
position: absolute;
width: 20px;
height: 20px;
top: 20px;
right: 20px;
opacity: 0.8;
transition: all 200ms;
font-size: 24px;
font-weight: bold;
text-decoration: none;
color: #666;
}
.popup .close:hover {
opacity: 1;
}
.popup .content {
max-height: 400px;
overflow: auto;
}
.popup p {
margin: 0 0 1em;
}
.popup p:last-child {
margin: 0;
}
iframe {
border: none;
}
<html>
<head>
<meta charset="UTF-8">
<meta content='width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0' name='viewport'>
</head>
<body>
<div id="center">
<div id="wrapper">
<p><a class="button" href="#popup1">Click Me</a></p>
</div>
<div id="popup1" class="overlay">
<div class="popup">
<h2>Drop Day</h2>
<a class="close" href="#">×</a>
<div class="content">
<p>Hello</p>
</div>
</div>
</div>
</div>
</body>
</html>