Если кому-то нужно. 100%
html,
body {
margin: 0;
padding: 0;
}
body {
width: 380px;
min-height: 280px;
padding: 10px;
font-family: “Arial”, sans-serif;
font-size: 14px;
line-height: 1.4;
background: #ecf0f1;
}
.main-menu {
margin:0;
padding: 0;
list-style:none;
width: 200px;
}
.main-menu li {
background-color: #2980b9;
border-bottom: 2px solid #2c3e50;
}
.main-menu li a {
display: block;
padding: 10px 15px;;
color: #fff;
text-decoration: none;
}
.main-menu .opened {
background-color: #1abc9c;
position: relative;
}
.main-menu .opened ul {
margin:0;
padding:0;
list-style: none;
position: absolute;
left: 180px;
top: 0px;
}
.main-menu .opened ul li {
background-color: #1abc9c;
border-bottom: 2px solid #2ecc71;
width: 200px;
}
.main-menu .opened ul li a {
display: block;
}