*{
    padding: 0;
    margin: 0;
    box-sizing: border-box;
    font-family: 'lato';
    list-style: none;
    text-decoration: none;
}
body{
    background-color: #fcdc29;
    display: flex;
    justify-content: center;
    align-items: center;
    margin-top: 200px
}
.main{
    width: 250px;
    display: block;
    border-radius: 10px;
    overflow: hidden;
}
.item{
    border-top: 1px solid #ef584a;
    overflow: hidden;
}
.btn{
    display: block;
    position: relative;
    padding: 15px 20px;
    background-color: #ff6f61;
    color: #fff; 
}
.btn i {
    margin-right: 10px;
}
.subitem{
    background: #273057;
    overflow: hidden;
    transition: max-height 0.7s;
    max-height: 0;
}
.subitem a{
    display: block;
    padding: 15px 20px;
    color: #fff;
    font-size: 14px;
    border-bottom: 1px solid #394c7f;
    position: relative;
}
.subitem a:before{
    content: '';
    opacity: 0;
    transition: opacity 0.3s;
}
.subitem a:hover:before{
    content: '';
    opacity: 1;
    transition: opacity 0.3s;
    border-top: 24px solid transparent;
    border-left: 11px solid #fcdc29;
    border-bottom: 24px solid transparent;
    position: absolute;
    width: 6px;
    height: 0;
    left: 0;
    top:0;
}
.subitem a:after{
    content: '';
    opacity: 0;
    transition: opacity 0.3s;
}
.subitem a:hover:after{
    content: '';
    opacity: 1;
    transition: opacity 0.3s;
    border-top: 24px solid transparent;
    border-right: 11px solid #fcdc29;
    border-bottom: 24px solid transparent;
    position: absolute;
    width: 6px;
    height: 0;
    right: 0;
    top:0;
}
.subitem a:hover{
    background: linear-gradient(to bottom, #273057 0%,#273057 50%,#394c7f 51%,#394c7f 100%);
    transition: all 0.3s ease-in-out;
    border-bottom: 0px solid #394c7f;
}
.item:target .subitem{
    max-height: 200px;
}