menu.css

body {
    background-color:  rgb(13, 1, 39);
    margin: 0;
    color: white;
}

header {
    padding: 10px;
    text-align: center;
}

h1{
    text-align: center;
    font-family: 'Lucida Sans', 'Lucida Sans Regular', 'Lucida Grande', 'Lucida Sans Unicode', Geneva, Verdana, sans-serif;
}

.content {
    max-width: 800px;
    margin: 0 auto;
}

#btn_open {
    cursor: pointer;
    transition: all 0.5s;
    display: flex;
    justify-content: left;
}

#btn_open:hover {
    cursor: pointer;
}

#btn_close{
    padding: 10px;
}

.menu {
    position: fixed;
    top: 0;
    width: 250px;
    height: 100%;
    background-color: black;
}

.menu ul {
    list-style: none;
}

.menu ul li {
    display: block;
}

.menu ul li a {
    transition: background 0.3s;
    display: block;
    color: white;
    font-size: 19px;
    text-decoration: none;
    text-transform: uppercase;
    padding: 10px 15px;
}

.effect {
    transition: margin 0.4s;
}