z-index for position:fixed?

Question

Please tell me how to apply z-index if the covering element must have position: fixed? In this case, position:fixed; is applied to navigation, but it is on top of it that I need to display the menu button. How can this be done?

Here is my example, correctly displayed at full page.

Previously, I was helped in explaining how z-index works in this example, but there was no such condition as position:fixed.

  $('#nav-btn').on('click', function () {
    $('#nav-btn').toggleClass('open');
    $('.navigation').toggleClass('is-opened');
  });

.navigation.is-opened {
    opacity: 1;
    pointer-events: auto;
    transition: opacity 0s 0s;
}

.navigation.is-opened .navigation__inner {
    -webkit-transform: translateX(0%);
    transform: translateX(0%);
}

.navigation {
    position: fixed;
    width: 100%;
    right: 0;
    top: 0;
    bottom: 0;
    opacity: 0;
    z-index: 150;
    pointer-events: none;
    overflow: hidden;
    text-align: center;
    color: #fff;
    display: block;
    transition: opacity 0s 0.3s;
    -webkit-overflow-scrolling: touch;
}

.navigation__inner {
    background-color: #0c1428;
    height: 100%;
    position: relative;
    width: 223px;
    margin-left: auto;
    max-width: 100%;
    display: -ms-flexbox;
    display: flex;
    -ms-flex-direction: column;
    flex-direction: column;
    -webkit-transform: translateX(100%);
    transform: translateX(100%);
    transition: -webkit-transform 0.3s;
    transition: transform 0.3s;
    transition: transform 0.3s, -webkit-transform 0.3s;
}

.navigation__header {
    background-color: #0c1428;
    position: absolute;
    left: 0;
    right: 0;
    top: 0;
    height: 80px;
    z-index: 1;
    padding: 80px 0 0;
    display: -ms-flexbox;
    display: flex;
    -ms-flex-align: center;
    align-items: center;
    -ms-flex-pack: center;
    justify-content: center;
    width: auto;
}

.navigation__content {
    padding-top: 80px;
    height: 100%;
    position: relative;
}

* {
    min-width: 0;
    min-height: 0;
    -webkit-tap-highlight-color: rgba(0,0,0,0);
}

.navigation__menu {
    position: absolute;
    left: 0;
    top: 180px;
    right: 0;
    bottom: 0;
    overflow: hidden;
    padding: 40px 20px 40px 40px;
    -webkit-overflow-scrolling: touch;
}

.navigation__content {
    padding-top: 80px;
    height: 100%;
    position: relative;
}

.head-panel {
    height: calc(100vh - 217px);
    position: relative;
}

.head-panel__slider-wr {
    position: absolute;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
}

}
.head-panel__slider {
    opacity: 1 !important;
}

.head-panel__content {
    position: relative;
    z-index: 1;
}

.head-panel__list {
    position: relative;
    display: -ms-flexbox;
    display: flex;
    -ms-flex-wrap: wrap;
    flex-wrap: wrap;
    height: calc(100vh - 217px);
}

.head-panel__section--center {
    position: relative;
    -ms-flex: 1 1;
    flex: 1 1;
    text-align: right;
    padding: 66px 297px;
    box-sizing: border-box;
}

.head-panel__section--last {
    padding: 64px 32px;
    box-sizing: border-box;
    background: rgba(12,20,40,0.24);
    display: -ms-flexbox;
    display: flex;
    -ms-flex-direction: column;
    flex-direction: column;
    -ms-flex-pack: justify;
    justify-content: space-between;
    -ms-flex-align: center;
    align-items: center;
    max-width: 223px;
    min-width: 223px;
}

#nav-btn {
    width: 24px;
    height: 24px;
    position: relative;
    -webkit-transform: rotate(0deg);
    -moz-transform: rotate(0deg);
    -o-transform: rotate(0deg);
    transform: rotate(0deg);
    -webkit-transition: 0.5s ease-in-out;
    -moz-transition: 0.5s ease-in-out;
    -o-transition: 0.5s ease-in-out;
    transition: 0.5s ease-in-out;
    cursor: pointer;
    z-index: 10;
}

#nav-btn {
  width: 24px;
  height: 24px;
  position: relative;
  -webkit-transform: rotate(0deg);
  -moz-transform: rotate(0deg);
  -o-transform: rotate(0deg);
  transform: rotate(0deg);
  -webkit-transition: 0.5s ease-in-out;
  -moz-transition: 0.5s ease-in-out;
  -o-transition: 0.5s ease-in-out;
  transition: 0.5s ease-in-out;
  cursor: pointer;
  z-index: 10;
}

#nav-btn span {
  display: block;
  position: relative;
  height: 3px;
  width: 100%;
  background: #fff;
  border-radius: 9px;
  opacity: 1;
  left: 0;
  -webkit-transform: rotate(0deg);
  -moz-transform: rotate(0deg);
  -o-transform: rotate(0deg);
  transform: rotate(0deg);
  -webkit-transition: 0.5s ease-in-out;
  -moz-transition: 0.5s ease-in-out;
  -o-transition: 0.5s ease-in-out;
  transition: 0.5s ease-in-out;
  z-index: 999;
}

#nav-btn span:nth-child(1) {
  top: 0px;
  -webkit-transform-origin: left center;
  -moz-transform-origin: left center;
  -o-transform-origin: left center;
  transform-origin: left center;
}

#nav-btn span:nth-child(2) {
  top: 7px;
  -webkit-transform-origin: left center;
  -moz-transform-origin: left center;
  -o-transform-origin: left center;
  transform-origin: left center;
}

#nav-btn span:nth-child(3) {
  top: 14px;
  width: 70%;
  -webkit-transform-origin: left center;
  -moz-transform-origin: left center;
  -o-transform-origin: left center;
  transform-origin: left center;
}

#nav-btn.open span:nth-child(1) {
  will-change: transform;
  -webkit-transform: rotate(-45deg);
  -moz-transform: rotate(-45deg);
  -o-transform: rotate(-45deg);
  transform: rotate(-45deg);
  will-change: transform;
  top: 18px;
  width: 30px;
}

#nav-btn.open span:nth-child(2) {
  will-change: transform;
  -webkit-transform: rotate(30deg);
  -moz-transform: rotate(45deg);
  -o-transform: rotate(45deg);
  transform: rotate(45deg);
  will-change: transform;
  top: -3px;
  width: 30px;
}

#nav-btn.open span:nth-child(3) {
  width: 0%;
  opacity: 0;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<!DOCTYPE html>
<html>
<head>
	<title></title>
</head>
<body class="app home">
	<div class="navigation">
		<div class="navigation__inner">
			<div class="navigation__header">
			</div>
			<div class="navigation__content">
				<div class="navigation__menu">
				</div>
			</div>
		</div>
	</div><!-- b:navigation -->
	<header class="app-header mt-4">
		<div class="head-panel">
			<div class="head-panel__slider-wr">
				<div class="head-panel__slider animator-zoomOfferScale animator owl-carousel owl-loaded" data-animator="zoomOfferScale"></div>
				<div class="head-panel__content">
					<div class="head-panel__list">
						<div class="head-panel__section head-panel__section--center animator-s9 animator-fadeInRight animator" data-animator="fadeInRight"></div>
						<div class="head-panel__section head-panel__section--last animator-s1 animator-fadeInRightBig animator" data-animator="fadeInRightBig">
							<div class="" id="nav-btn">
								<span></span> <span></span> <span></span>
							</div>
						</div>
					</div>
				</div>
			</div><!-- b:head-panel -->
		</div>
	</header>
</body>
</html>

Answer 1

You are on right track just put z-index on parent container like below

.head-panel {
    z-index: 222;
}

As head-panel is first parent of your header.

$('#nav-btn').on('click', function () {
    $('#nav-btn').toggleClass('open');
    $('.navigation').toggleClass('is-opened');
  });

.navigation.is-opened {
    opacity: 1;
    pointer-events: auto;
    transition: opacity 0s 0s;
}

.navigation.is-opened .navigation__inner {
    -webkit-transform: translateX(0%);
    transform: translateX(0%);
}

.navigation {
    position: fixed;
    width: 100%;
    right: 0;
    top: 0;
    bottom: 0;
    opacity: 0;
    z-index: 150;
    pointer-events: none;
    overflow: hidden;
    text-align: center;
    color: #fff;
    display: block;
    transition: opacity 0s 0.3s;
    -webkit-overflow-scrolling: touch;
}

.navigation__inner {
    background-color: #0c1428;
    height: 100%;
    position: relative;
    width: 223px;
    margin-left: auto;
    max-width: 100%;
    display: -ms-flexbox;
    display: flex;
    -ms-flex-direction: column;
    flex-direction: column;
    -webkit-transform: translateX(100%);
    transform: translateX(100%);
    transition: -webkit-transform 0.3s;
    transition: transform 0.3s;
    transition: transform 0.3s, -webkit-transform 0.3s;
}

.navigation__header {
    background-color: #0c1428;
    position: absolute;
    left: 0;
    right: 0;
    top: 0;
    height: 80px;
    z-index: 1;
    padding: 80px 0 0;
    display: -ms-flexbox;
    display: flex;
    -ms-flex-align: center;
    align-items: center;
    -ms-flex-pack: center;
    justify-content: center;
    width: auto;
}

.navigation__content {
    padding-top: 80px;
    height: 100%;
    position: relative;
}

* {
    min-width: 0;
    min-height: 0;
    -webkit-tap-highlight-color: rgba(0,0,0,0);
}

.navigation__menu {
    position: absolute;
    left: 0;
    top: 180px;
    right: 0;
    bottom: 0;
    overflow: hidden;
    padding: 40px 20px 40px 40px;
    -webkit-overflow-scrolling: touch;
}

.navigation__content {
    padding-top: 80px;
    height: 100%;
    position: relative;
}

.head-panel {
    height: calc(100vh - 217px);
    position: relative;
    z-index: 222;
}

.head-panel__slider-wr {
    position: absolute;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
}

}
.head-panel__slider {
    opacity: 1 !important;
}

.head-panel__content {
    position: relative;
    z-index: 1;
}

.head-panel__list {
    position: relative;
    display: -ms-flexbox;
    display: flex;
    -ms-flex-wrap: wrap;
    flex-wrap: wrap;
    height: calc(100vh - 217px);
}

.head-panel__section--center {
    position: relative;
    -ms-flex: 1 1;
    flex: 1 1;
    text-align: right;
    padding: 66px 297px;
    box-sizing: border-box;
}

.head-panel__section--last {
    padding: 64px 32px;
    box-sizing: border-box;
    background: rgba(12,20,40,0.24);
    display: -ms-flexbox;
    display: flex;
    -ms-flex-direction: column;
    flex-direction: column;
    -ms-flex-pack: justify;
    justify-content: space-between;
    -ms-flex-align: center;
    align-items: center;
    max-width: 223px;
    min-width: 223px;
}

#nav-btn {
    width: 24px;
    height: 24px;
    position: relative;
    -webkit-transform: rotate(0deg);
    -moz-transform: rotate(0deg);
    -o-transform: rotate(0deg);
    transform: rotate(0deg);
    -webkit-transition: 0.5s ease-in-out;
    -moz-transition: 0.5s ease-in-out;
    -o-transition: 0.5s ease-in-out;
    transition: 0.5s ease-in-out;
    cursor: pointer;
    z-index: 10;
}

#nav-btn {
  width: 24px;
  height: 24px;
  position: relative;
  -webkit-transform: rotate(0deg);
  -moz-transform: rotate(0deg);
  -o-transform: rotate(0deg);
  transform: rotate(0deg);
  -webkit-transition: 0.5s ease-in-out;
  -moz-transition: 0.5s ease-in-out;
  -o-transition: 0.5s ease-in-out;
  transition: 0.5s ease-in-out;
  cursor: pointer;
  z-index: 10;
}

#nav-btn span {
  display: block;
  position: relative;
  height: 3px;
  width: 100%;
  background: #fff;
  border-radius: 9px;
  opacity: 1;
  left: 0;
  -webkit-transform: rotate(0deg);
  -moz-transform: rotate(0deg);
  -o-transform: rotate(0deg);
  transform: rotate(0deg);
  -webkit-transition: 0.5s ease-in-out;
  -moz-transition: 0.5s ease-in-out;
  -o-transition: 0.5s ease-in-out;
  transition: 0.5s ease-in-out;
  z-index: 999;
}

#nav-btn span:nth-child(1) {
  top: 0px;
  -webkit-transform-origin: left center;
  -moz-transform-origin: left center;
  -o-transform-origin: left center;
  transform-origin: left center;
}

#nav-btn span:nth-child(2) {
  top: 7px;
  -webkit-transform-origin: left center;
  -moz-transform-origin: left center;
  -o-transform-origin: left center;
  transform-origin: left center;
}

#nav-btn span:nth-child(3) {
  top: 14px;
  width: 70%;
  -webkit-transform-origin: left center;
  -moz-transform-origin: left center;
  -o-transform-origin: left center;
  transform-origin: left center;
}

#nav-btn.open span:nth-child(1) {
  will-change: transform;
  -webkit-transform: rotate(-45deg);
  -moz-transform: rotate(-45deg);
  -o-transform: rotate(-45deg);
  transform: rotate(-45deg);
  will-change: transform;
  top: 18px;
  width: 30px;
}

#nav-btn.open span:nth-child(2) {
  will-change: transform;
  -webkit-transform: rotate(30deg);
  -moz-transform: rotate(45deg);
  -o-transform: rotate(45deg);
  transform: rotate(45deg);
  will-change: transform;
  top: -3px;
  width: 30px;
}

#nav-btn.open span:nth-child(3) {
  width: 0%;
  opacity: 0;
}

.app-header{
z-index: 222;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<!DOCTYPE html>
<html>
<head>
	<title></title>
</head>
<body class="app home">
	<div class="navigation">
		<div class="navigation__inner">
			<div class="navigation__header">
			</div>
			<div class="navigation__content">
				<div class="navigation__menu">
				</div>
			</div>
		</div>
	</div><!-- b:navigation -->
	<header class="app-header mt-4">
		<div class="head-panel">
			<div class="head-panel__slider-wr">
				<div class="head-panel__slider animator-zoomOfferScale animator owl-carousel owl-loaded" data-animator="zoomOfferScale"></div>
				<div class="head-panel__content">
					<div class="head-panel__list">
						<div class="head-panel__section head-panel__section--center animator-s9 animator-fadeInRight animator" data-animator="fadeInRight"></div>
						<div class="head-panel__section head-panel__section--last animator-s1 animator-fadeInRightBig animator" data-animator="fadeInRightBig">
							<div class="" id="nav-btn">
								<span></span> <span></span> <span></span>
							</div>
						</div>
					</div>
				</div>
			</div><!-- b:head-panel -->
		</div>
	</header>
</body>
</html>