I want to keep my header fixed in place like this:

And then I want to add the body content below the header:
<div>
<Header />
<br />
<br />
<br />
<br />
<div style={{ color: 'red', zIndex: 101 }}>Hello World</div>
</div>
However in order to keep this responsive, I can't just go with some manual calculation like marginTop: '10rem' as based on different screen sizes it may vary. I want to know what's the best way around to deal with this?
Here's how I have styled my header:
.Header {
position: fixed;
top: 0;
left: 0;
width: 100%;
background: $light-bg;
box-shadow: -4px 4px 10px 7px rgba(0, 0, 0, 0.25);
padding: 0 1rem;
display: flex;
justify-content: space-between;
align-items: center;
animation-duration: $background-animation-duration;
animation-name: animateFadeEffectLight;
animation-timing-function: ease-in;
&_dark {
background: $toggle-switch-color-dark;
animation-duration: $background-animation-duration;
animation-name: animateFadeEffectDark;
animation-timing-function: ease-in;
}
}
Here's how my layout looks like:
<div>
<Header />
<div style={{ color: 'red', zIndex: 101 }}>Hello World</div>
</div>
