Setting text to stay above another element at all times - html

Question

I have one regular box and I wish the text to float above it and resize the text's font size appropriately.
This is what I have done: https://jsfiddle.net/a87uo3t2/
#import url('https://fonts.googleapis.com/css?family=Share+Tech+Mono');
body {
margin: 0 auto;
overflow: hidden;
}
#content {
width: 100%;
height: 2527px;
background-image: url('../images/wallpaper.jpg');
}
#menu-container,
#button-container {
position: absolute;
top: 0;
bottom: 0;
left: 0;
right: 0;
margin: auto;
width: 30%;
height: 40%;
border: 1px line #ccc;
background-color: #ffffff;
background-image: url('../images/brick-wall.png');
box-shadow: 0 0 3em #ccc;
}
#button-container {
border: none;
box-shadow: none;
}
.button-sub-container {
display: inline-flex;
flex-direction: column;
justify-content: center;
align-items: center;
}
h1 {
position: relative;
bottom: 120px;
left: 6px;
text-align: center;
font-family: 'Share Tech Mono', monospace;
font-size: 5vw;
text-transform: uppercase;
text-decoration: none;
letter-spacing: 15px;
}
/*BUTTONS*/
.main-button {
text-decoration: none;
font-family: 'Share Tech Mono', monospace;
font-size: 35px;
margin: 15px;
color: #000;
letter-spacing: 5px;
text-transform: uppercase;
transition: letter-spacing 0.5s, color 0.8s;
}
.main-button:hover {
letter-spacing: 15px;
color: red;
}
.main-button:active {
letter-spacing: 2px;
color: blue;
}
<div id="content">
<div id="menu-container">
<h1>welcome</h1>
<div id="button-container" class="button-sub-container">
<a class="main-button" href="about.html">about</a>
<a class="main-button" href="projects.html">projects</a>
<a class="main-button" href="contact.html">contact</a>
</div>
</div>
As you can see I have tried setting it on top by positioning it relatively yet this means upon resizing it shifts, I can fix this by using vw as font size to a point, since if one would have a very wide monitor, it would go over my small menu-container.
Side-Note: don't bring attention to the buttons-text breaking out of the box, I have a a media-key to fix that

Answer 1

A solution with flexbox
and changing only the font-size of the box
#import url('https://fonts.googleapis.com/css?family=Share+Tech+Mono');
html,
body {
height: 100%;
}
body {
margin: 0;
display: flex;
justify-content: center;
align-items: center;
}
.box {
font-family: 'Share Tech Mono', monospace;
max-width: 50%;
text-align: center;
/* Change to your needs */
font-size: 20px;
}
.box h1 {
text-transform: uppercase;
margin-top: 0;
}
.box ul {
list-style: none;
margin: 0;
padding: 15px;
border: 1px line #ccc;
background-color: #ffffff;
background-image: url('../images/brick-wall.png');
box-shadow: 0 0 3em #ccc;
}
.box a {
text-decoration: none;
color: #000;
text-transform: uppercase;
white-space: nowrap;
transition: letter-spacing 0.5s, color 0.8s;
}
.box a:hover {
letter-spacing: 3px;
color: red;
}
/* Change to your needs */
#media screen and (min-width: 600px) {
.box {
font-size: 20px;
}
}
/* Change to your needs */
#media screen and (min-width: 1200px) {
.box {
font-size: 30px;
}
}
<div class="box">
<h1>Heading</h1>
<!-- It's a list -->
<ul>
<li>Site 1</li>
<li>Site 2</li>
<li>Site 3</li>
</ul>
</div>