Is there a way to make an overlay over content when sidebar is open without using JavaScript?

Issue

I have a sidebar on my page but I can't figure out a good way to make an overlay over the main content when it is open without JavaScript. Is it possible? And if not how would I go about doing it with JavaScript?

The easiest way to make a sidebar seems to be with an input checkbox like below, but I don't know if that constrains me in regards to doing what I want. I'm thinking maybe it would be easier using only JavaScript?

I apologize in advance if this is a dumb question but I don't know how to fix it and would really appreciate some help.

Here's a fiddle with my code:

https://jsfiddle.net/putyj6rv/

And my HTML because SO so desperately wants some code:

<section class='navbar'>
    <div class='navbar-container'>
            <div id="sidebarContainer" class=''>
            <input type="checkbox" aria-label='Toggle navigation' class="openSideMenu" id="openSideMenu">
                <label for="openSideMenu" class="sideIconToggle">
                    <div class="spinner diagonal part-1"></div>
                    <div class="spinner horizontal"></div>
                    <div class="spinner diagonal part-2"></div>
                </label>
                <div id="sideMenu">
                    <ul class="sideMenuInner">
                        <li class="active" onclick="hideSidebar()"><a href="#" data-toggle="tab">Item1</a></li>
                        <li onclick="hideSidebar()"><a href="#" data-toggle="tab">Item2</a></li>
                        <li onclick="hideSidebar()"><a href="#" data-toggle="tab">Item3</a></li>
                    </ul>
                </div>
            </div>
    </div>
</section>
<div class='main'>
How can I get an overlay to appear / fade in/out over this area when the sidebar is open?

</div>

Solution

Here is a simple CSS hamburger menu for you. The functionality of this CSS hamburger menu relies on shifting the opacity and the location of information utilizing CSS transitions and transforms.

I also added an div labelled overlay which hides the main content with a blur effect when the checkbox is clicked.

I also linked a list of 16 other hamburger menu designs you could also utilize.

body {
  margin: 0;
  padding: 0;
  background: #232323;
  color: #cdcdcd;
  font-family: Helvetica, Arial, sans-serif;
}

main {
  margin: 10vw;
  z-index: 0;
}

.hamburger-menu-toggle {
  display: block;
  position: relative;
  top: 50px;
  left: 50px;
  z-index: 3;
  user-select: none;
}

.hamburger-menu-toggle a {
  text-decoration: none;
  color: #232323;
  transition: color 0.3s ease;
}

.hamburger-menu-toggle a:hover {
  color: tomato;
}

.hamburger-menu-toggle input {
  display: block;
  width: 40px;
  height: 32px;
  position: absolute;
  top: -7px;
  left: -5px;
  cursor: pointer;
  opacity: 0;
  z-index: 4;
  -webkit-touch-callout: none;
}



.hamburger-menu {
  position: absolute;
  width: 300px;
  margin: -100px 0 0 -50px;
  padding: 50px;
  padding-top: 125px;
  background: #ededed;
  list-style-type: none;
  transform-origin: 0% 0%;
  transform: translate(-100%, 0);
  transition: transform 0.5s cubic-bezier(0.77, 0.2, 0.05, 1.0);
  z-index: 2;
}

.hamburger-menu li {
  padding: 10px 0;
  font-size: 22px;
}

.hamburger-menu-toggle input:checked~.hamburger-menu {
  transform: none;
}

.overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.5);
  backdrop-filter: blur(8px);
  z-index: 1;
  transition: opacity 0.5s;
  opacity: 0;
}

.hamburger-menu-toggle input:checked~.overlay {
  opacity: 1;
}

.hamburger-menu-toggle span {
  display: block;
  width: 33px;
  height: 4px;
  margin-bottom: 5px;
  position: relative;
  background: #cdcdcd;
  border-radius: 3px;
  z-index: 3;
  transform-origin: 4px 0px;
  transition: transform 0.5s cubic-bezier(0.77, 0.2, 0.05, 1.0), background 0.5s cubic-bezier(0.77, 0.2, 0.05, 1.0), opacity 0.33s ease;
}

.hamburger-menu-toggle span:first-child {
  transform-origin: 0% 0%;
}

.hamburger-menu-toggle span:nth-last-child(2) {
  transform-origin: 0% 100%;
}

.hamburger-menu-toggle input:checked~span {
  opacity: 1;
  transform: rotate(45deg) translate(-2px, -1px);
  background: #232323;
}

.hamburger-menu-toggle input:checked~span:nth-last-child(3) {
  opacity: 0;
  transform: rotate(0deg) scale(0.2, 0.2);
}

.hamburger-menu-toggle input:checked~span:nth-last-child(4) {
  transform: rotate(-45deg) translate(-6px, 2px);
}

<body>
  <nav role="navigation">
    <div class="hamburger-menu-toggle">
      <input type="checkbox" />
      <span></span>
      <span></span>
      <span></span>
      <ul class="hamburger-menu">
        <a href="#">
          <li>Item 1</li>
        </a>
        <a href="#">
          <li>Item 2</li>
        </a>
        <a href="#">
          <li>Item 3</li>
        </a>
      </ul>
      <div class="overlay"></div>
    </div>
  </nav>
  <main>
    <p>How can I get an overlay to appear / fade in/out over this area when the sidebar is open?
      <p>
  </main>
</body>

Answered By - Nick Friesen