How to implement a drop down list on menu button click on small screens with just CSS?

Question

css

<div class="menu-wrapper">
            <div class="menu">
                <div class="navi">
                    <div class="burger">
                        <hr>
                        <hr>
                        <hr>
                    </div>
                    <ul>
                        <li><a href="#">О компании</a></li>
                        <li><a href="#">Доставка</a></li>
                        <li><a href="#">Рассрочка</a></li>
                        <li><a href="#">Адреса магазинов</a></li>
                        <li><a href="#">Покупателю</a></li>
                        <li><a href="#">Отзывы</a></li>
                        <div class="clearfix"></div>
                    </ul>
                </div>
                <div class="social">
                    <a href="#"><i class="fa fa-vk fa-lg" aria-hidden="true"></i></a>
                    <a href="#"><i class="fa fa-facebook fa-lg" aria-hidden="true"></i></a>
                    <a href="#"><i class="fa fa-twitter fa-lg" aria-hidden="true"></i></a>
                    <a href="#"><i class="fa fa-envelope-o fa-lg" aria-hidden="true"></i></a>
                </div>
                <div class="clearfix"></div>
            </div>
            <div class="menu-mobile">
                <ul>
                    <li><a href="#">О компании</a></li>
                    <li><a href="#">Доставка</a></li>
                    <li><a href="#">Рассрочка</a></li>
                    <li><a href="#">Адреса магазинов</a></li>
                    <li><a href="#">Покупателю</a></li>
                    <li><a href="#">Отзывы</a></li>
                </ul>
            </div>
        </div>

.menu-wrapper{
    font-family: 'Open Sans', sans-serif;
    width: 100%;
    background-color: #232323;
    background-size: cover;
}
.menu{
    width: 96%;
    padding: 20px 2%;
    max-width: 1280px;
    margin: auto;
}
/*Навигация*/
.navi{
    float: left;
    width: 75%;
}
.burger{
    display: none;
    width: 30px;
    cursor: pointer;
    padding: 5px;
}
.burger hr{
    margin: 5px 10%;
    width: 80%;
    color: #FE2B2B;
    height: 2px;
    background-color: #FE2B2B;
    border: 0;
}
.navi ul li{
    margin-right: 65px;
    font-size: 14px;
    font-weight: bold;
    float: left;
}
.navi ul li a{
    -webkit-transition: all 200ms ease;
    -moz-transition: all 200ms ease;
    -o-transition: all 200ms ease;
    -ms-transition: all 200ms ease;
    transition: all 200ms ease;
    text-decoration: none;
    color: #FFFFFF;
}
.navi ul li a:hover{
    color: #FE2B2B;
}
/*Адаптивная навигация*/
.menu-mobile{
    width: 96%;
    padding: 10px 2%;
    max-width: 1280px;
    margin: auto;
    display: none;
}
.menu-mobile ul{
    text-align: center;
}
.menu-mobile ul li{
    padding: 5px;
    
}
.menu-mobile ul li a{
    font-weight: bold;
    color: #FFFFFF;
    text-decoration: none;
    -webkit-transition: all 200ms ease;
    -moz-transition: all 200ms ease;
    -o-transition: all 200ms ease;
    -ms-transition: all 200ms ease;
    transition: all 200ms ease;
}
.menu-mobile ul li a:hover{
    color: #FE2B2B;
}
.burger:hover .menu-mobile{
    display: block;
}
/*Иконки социальных сетей*/
.social{
    float: right;
    width: 25%;
    margin-top: -4px;
}
.social i{
    color: #FFFFFF;
    margin-left: 50px;
    -webkit-transition: all 200ms ease;
    -moz-transition: all 200ms ease;
    -o-transition: all 200ms ease;
    -ms-transition: all 200ms ease;
    transition: all 200ms ease;
}
.social i:hover{
    color: #FE2B2B;
}
.clearfix{
    clear: both;
}


/*Стили для навигации*/

@media screen and (max-width:1269px){
    .navi ul li{
        margin-right: 60px;
    }
}
@media screen and (max-width:1224px){
    .navi ul li{
        margin-right: 50px;
    }
    .social i{
        margin-left: 40px;
    }
}
@media screen and (max-width:1142px){
    .navi ul li{
        margin-right: 40px;
    }
}
@media screen and (max-width:1060px){
    .navi ul li{
        margin-right: 30px;
    }
    .social i{
        margin-left: 30px;
    }
}
@media screen and (max-width:977px){
    .navi ul li{
        margin-right: 25px;
    }
}
@media screen and (max-width:933px){
    .navi ul li{
        margin-right: 15px;
    }
    .social i{
        margin-left: 20px;
    }
}
@media screen and (max-width:870px){
    .social i{
        margin-left: 20px;
    }
}
@media screen and (max-width:850px){
    .social i{
        margin-left: 15px;
    }
    .navi ul li{
        font-size: 13px;
        margin-right: 12px;
    }
}
@media screen and (max-width:810px){
    .social i{
        margin-left: 10px;
    }
    .navi ul li{
        margin-right: 10px;
    }
}
@media screen and (max-width:790px){
    .burger{
        display: block;
    }
    .navi{
        width: 60%;
    }
    .navi ul li{
        display: none;
    }
    .social{
        width: 40%;
    }
    .social i{
        margin-top: 12px;
        margin-left: 35px;
    }
}
@media screen and (max-width:630px){
    .social i{
        margin-left: 25px;
    }
}
@media screen and (max-width:510px){
    .social i{
        margin-left: 15px;
    }
}
@media screen and (max-width:410px){
    .navi{
        width: 40%;
    }
    .social{
        width: 60%;
    }
    .social i{
        margin-left: 20px;
    }
}

There is a class="burger" button. It is necessary that when you click on it, the menu list class="menu-mobile" drops out. On large screens, the list is hidden, I tried to use the Focus pseudo-class for the button, but it does not react at all, maybe the problem is in the markup itself?

Answer 1

1/ It's not a button, it's a simple div, it has no focus.
2. Better to use js

Answer 2

A dropdown menu in pure css is done through a checkbox hack. Googled in 20 seconds) But IMHO it's much faster to write the same thing in js/jquery. There business for 5 minutes along with reading the methodology.

Answer 3

JavaScript. Google it, there are tons of answers to this question.