Отзывчное меню боковой панели с использованием Pure HTML & CSS.

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    list-style: none;
    text-decoration: none;
}
body{
    overflow: hidden;
    font-family: sans-serif; 
    background-color: #387b6a;
    height: 100vh;  
}

.menu{
    height: 100%;
    position: fixed;
    left: 0;
    top: 0;
    width: 250px;
    padding-top: 60px;
    background-color: #212121; 
    transition: 0.5s;
    transform: translateX(-250px);
}
.logo a{
    padding: 15px 25px;
    font-size: 40px;
    text-transform: uppercase;
    color: white;
    /*margin-left: 5px*/
}
.logo a img{
    max-width:140px;
    border-radius: 50%;
    margin-bottom: 10px;
}
ul li{
    border-bottom: 1px solid rgba(255, 255, 255, 0.10);
    transition: 0.3s;
    /*text-align: center;*/
    padding-left: 25px;
}
ul li:hover{
    padding-left: 35px;
    background-color: #445665;
}
ul li a{
    display: block;
    color: #fff;
    padding: 20px;
    text-transform: uppercase;
    font-weight: bold;
}

#open{
    display: none;
}
.open{
    height: 80px
    width: 80px;
    /*position: absolute;*/
    /*background-color: #000;*/
}
.open i{
    font-size: 25px;
    cursor: pointer;
    margin-left: 25px;
    margin-top: 25px;
    background-color: #000;
    padding: 15px 15px;
    color: white;
    z-index: 99;
}
#open:checked ~ .menu{
    transition: 0.5s;
    transform: translateX(0);
}
#open:checked ~ .open i{
    transition: 0.5s;
    margin-left: 190px;
    position: absolute;
}