Flexbox with center valign and allow expandable content - html

Question

First of all, the first snippet below is the problem I'm trying to fix.
Note that this was working perfectly fine IF display: flex; is applied to body.
However, I do not want to apply style to body which will break Google Web Cache layout.
* More explanation after the first snippet
* { box-sizing: border-box; }
body { margin: 0; }
.wrapper {
display: flex;
flex-direction: column;
min-height: 100vh;
width: 100%;
background-color: #ccc;
}
.navigation {
background-color: #f00;
width: 100%;
height: 3rem;
}
.footer {
background-color: #0f0;
width: 100%;
text-align: center;
line-height: 2rem;
}
.content {
background-color: #ff0;
flex: 1;
margin: 0.6rem 0 1.2rem;
}
.container {
background-color: #f0f;
margin: 0 auto;
max-width: 120rem;
width: 100%;
padding: 0 2rem;
}
.centered {
display: flex;
height: 100%;
align-items: center;
justify-content: center;
}
.long-content {
background-color: #fff;
}
<main class="wrapper">
<nav class="navigation">.navigation</nav>
<div class="content">
<section class="container centered">
<div class="long-content">.long-content</div>
</section>
</div>
<footer class="footer">.footer</footer>
</main>
So, removing display: flex; raised this issue:
section within .content does not have the height spanning across .content
Trying to fix it with position: relative on .content and position: absolute on .centered fixed the height issue but raised:
Width of .centered does not span across .content which can be easily fixed with left:0;right:0;
Height does not flow with content in section (I'm out of idea here)
Was it wrong to use position: relative and position: absolute to patch the original issue?
If so, what is the more suitable solution?
* { box-sizing: border-box; }
body { margin: 0; }
.wrapper {
display: flex;
flex-direction: column;
min-height: 100vh;
width: 100%;
background-color: #ccc;
}
.navigation {
background-color: #f00;
width: 100%;
height: 3rem;
}
.footer {
background-color: #0f0;
width: 100%;
text-align: center;
line-height: 2rem;
}
.content {
background-color: #ff0;
flex: 1;
margin: 0.6rem 0 1.2rem;
position: relative;
}
.container {
background-color: #f0f;
margin: 0 auto;
max-width: 120rem;
width: 100%;
padding: 0 2rem;
}
.centered {
display: flex;
position: absolute;
height: 100%;
left: 0;
right: 0;
align-items: center;
justify-content: center;
}
.long-content {
background-color: #fff;
height: 1000px;
}
<main class="wrapper">
<nav class="navigation">.navigation</nav>
<div class="content">
<section class="container centered">
<div class="long-content">.long-content</div>
</section>
</div>
<footer class="footer">.footer</footer>
</main>

Answer 1

I continued looking for solution and quickly noticed that I have shallow knowledge about flexbox itself so I went ahead and played with Flexbox Froggy.
After completing all the levels, I noticed that I can align everything without position: absolute by just using justify-content on .wrapper.
Below is my solution for my silly issue.
If you remove height of .long-content, .centered will continue to get aligned vertically.
Thank you froggies and shout out to Codepip!
* { box-sizing: border-box; }
body { margin: 0; }
.wrapper {
display: flex;
flex-direction: column;
min-height: 100vh;
width: 100%;
background-color: #ccc;
justify-content: space-between;
}
.navigation {
background-color: #f00;
width: 100%;
height: 3rem;
}
.footer {
background-color: #0f0;
width: 100%;
text-align: center;
line-height: 2rem;
}
.content {
background-color: #ff0;
margin: 0.6rem 0 1.2rem;
}
.container {
background-color: #f0f;
margin: 0 auto;
max-width: 120rem;
width: 100%;
padding: 0 2rem;
}
.centered {
display: flex;
height: 100%;
align-items: center;
justify-content: center;
}
.long-content {
background-color: #fff;
height: 1000px;
}
<main class="wrapper">
<nav class="navigation">.navigation</nav>
<div class="content">
<section class="container centered">
<div class="long-content">.long-content</div>
</section>
</div>
<footer class="footer">.footer</footer>
</main>