ヘッダーのデザインハンバーガー実装

<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>navgationの作成その1</title>
<link rel="stylesheet" href="css/style.css">
<link rel="stylesheet" href="css/hamburgers.css">
<style>
.hamburger-inner, .hamburger-inner::before, .hamburger-inner::after{
background-color: #FFF;
}
.hamburger.is-active .hamburger-inner, .hamburger.is-active .hamburger-inner::before, .hamburger.is-active .hamburger-inner::after{
background-color: #FFF;
}
</style>
</head>
<body>
<header>
<h1>FELICA</h1>
<p>未経験からプロになる!</p>
<nav id="g-nav">
<ul>
<li><a href="#">BLOG<span>ブログ</span></a></li>
<li><a href="#">SERVICE<span>サービス</span></a></li>
<li><a href="#">RECRUIT<span>採用情報</span></a></li>
<li><a href="#">COMPANY<span>会社案内</span></a></li>
<li><a href="#">CONTACT<span>お問い合わせ</span></a></li>
<li><input type="text"><a href="#">検索</a></li>
</ul>
</nav>
<p class="hamburger hamburger--stand" id="btn">
  <span class="hamburger-box">
    <span class="hamburger-inner"></span>
  </span>
</p>
</header>
<script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.0/jquery.min.js'></script>
<script>
$(function(){

//$('#g-nav').hide();

$('#btn').on('click',function(){
$(this).toggleClass('is-active');
$('#g-nav').fadeToggle(200);
});
});
</script>
</body>
</html>

style.css

@charset "utf-8";
html{box-sizing:border-box;-webkit-text-size-adjust:100%}*,:after,:before{background-repeat:no-repeat;box-sizing:inherit}:after,:before{text-decoration:inherit;vertical-align:inherit}*{padding:0;margin:0;box-sizing:border-box;}audio:not([controls]){display:none;height:0}hr{overflow:visible}article,aside,details,figcaption,figure,footer,header,main,menu,nav,section,summary{display:block}summary{display:list-item}small{font-size:80%}[hidden],template{display:none}abbr[title]{border-bottom:1px dotted;text-decoration:none}a{background-color:transparent;-webkit-text-decoration-skip:objects}a:active,a:hover{outline-width:0}code,kbd,pre,samp{font-family:monospace,monospace}b,strong{font-weight:bolder}dfn{font-style:italic}mark{background-color:#ff0;color:#000}sub,sup{font-size:75%;line-height:0;position:relative;vertical-align:baseline}sub{bottom:-.25em}sup{top:-.5em}input{border-radius:0}[role=button],[type=button],[type=reset],[type=submit],button{cursor:pointer}[disabled]{cursor:default}[type=number]{width:auto}[type=search]{-webkit-appearance:textfield}[type=search]::-webkit-search-cancel-button,[type=search]::-webkit-search-decoration{-webkit-appearance:none}textarea{overflow:auto;resize:vertical}button,input,optgroup,select,textarea{font:inherit}optgroup{font-weight:700}button{overflow:visible}[type=button]::-moz-focus-inner,[type=reset]::-moz-focus-inner,[type=submit]::-moz-focus-inner,button::-moz-focus-inner{border-style:0;padding:0}[type=button]::-moz-focus-inner,[type=reset]::-moz-focus-inner,[type=submit]::-moz-focus-inner,button:-moz-focusring{outline:1px dotted ButtonText}[type=reset],[type=submit],button,html [type=button]{-webkit-appearance:button}button,select{text-transform:none}button,input,select,textarea{background-color:transparent;border-style:none;color:inherit}select{-moz-appearance:none;-webkit-appearance:none}select::-ms-expand{display:none}select::-ms-value{color:currentColor}legend{border:0;color:inherit;display:table;max-width:100%;white-space:normal}::-webkit-file-upload-button{-webkit-appearance:button;font:inherit}[type=search]{-webkit-appearance:textfield;outline-offset:-2px}img{border-style:none;vertical-align: bottom}progress{vertical-align:baseline}svg:not(:root){overflow:hidden}audio,canvas,progress,video{display:inline-block}@media screen{[hidden~=screen]{display:inherit}[hidden~=screen]:not(:active):not(:focus):not(:target){position:absolute!important;clip:rect(0 0 0 0)!important}}[aria-busy=true]{cursor:progress}[aria-controls]{cursor:pointer}[aria-disabled]{cursor:default}::-moz-selection{background-color:#b3d4fc;color:#000;text-shadow:none}::selection{background-color:#b3d4fc;color:#000;text-shadow:none}ul,ol{list-style:none;}a{text-decoration:none;}.wrapper{overflow:hidden;}body{overflow-y:scroll;}img{max-width: 100%;}


header{
width: 100%;
height: 80px;
background-color: #333;
display: flex;
align-items: center;
color: #FFF;
padding: 0 40px;
}
h1{
margin-right: 20px;
}
header>p{
margin-right: auto;
}
#g-nav{
width: 60%;
}
#g-nav>ul{
display: flex;
}
#g-nav li{
width: 16.66%;
}
#g-nav a{
display: block;
height: 80px;
color: #FFF;
text-align: center;
padding-top: 26px;
font-weight: bold;
}
#g-nav span{
display: block;
font-size: 13px;
font-weight: normal;
}
#g-nav span::after{
display: block;
content: "";
width: 70%;
height: 4px;
margin: 0 auto;
background-color: #FFF;
transform: scale(0);
transition: 0.2s;
}
#g-nav a:hover>span::after{
transform: scale(1);
}
#g-nav li:last-of-type>a{
background: url(../img/icon.svg)no-repeat center center/30px;
white-space: nowrap;
text-indent: 100%;
overflow: hidden;
}
#g-nav a:hover>span{
/* text-decoration:4px underline;
text-underline-offset: 3px; */
}
input,#btn{
display: none;
}
@media (max-width:900px){
body{
height: 3000px;
}
header{
height: 60px;
position: fixed;
top: 0;
left: 0;
padding: 0 10px;
}
#g-nav{
width: 100%;
height: calc(100vh - 60px);
background-color: #344d6d;
position: fixed;
top: 60px;
left: 0;
padding:20px 40px;
}
#g-nav>ul{
display: block;
}
#g-nav li{
width: 100%;
}
#g-nav a{
height: 60px;
border-bottom: 1px solid #FFF;
}
#g-nav span{
display: inline;
margin-left: 10px;
}
#g-nav li:last-of-type{
display: flex;
padding-top: 20px;
}
#g-nav li:last-of-type>a{
width: 40px;
height: 40px;
background-color: #333;
border-bottom: 0;
}
#g-nav li:last-of-type>input{
background-color: #FFF;
width: calc(100% - 40px);
height: 40px;
display: block;
color: #222;
padding: 2px 4px;
}
#btn{
display: block;
}

}