* {
    margin: 0;
    padding: 0;
}

body {
    height: 100vh;
    background-color: #333;
}

.container {
    width: 15px;
    height: 600px;
    position: fixed;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    background-color: #222;
    border-radius: 0 15px 15px 0;
    overflow: hidden;
    transition: 0.3s;
    cursor: pointer;
}

.container:hover {
    width: 150px;
    border-radius: 0 30px 30px 0;
}

.container:hover li a {
    color: #fff;
}

.container::before {
    content: "";
    width: 50%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: -1;
    background-color: lightseagreen;
}

.container .top {
    width: calc(100% - 30px);
    margin-left: 30px;
    height: 20%;
    background-color: #222;
    border-radius: 0 0 0 20px;
    transition: 0.2s;
}

.container .middle {
    width: calc(100% - 60px);
    height: 10%;
    background-color: lightseagreen;
    margin-left: 40px;
    border-radius: 20px;
}

.container .bottom {
    width: calc(100% - 30px);
    height: 100%;
    margin-left: 30px;
    background-color: #222;
    border-radius: 20px 0 0 0;
}

.container li {
    position: absolute;
    top: var(--t);
    width: 100%;
    height: 10%;
    font-size: 30px;
    display: flex;
    justify-content: center;
    align-items: center;
}

.container li a {
    color: transparent;
    transition: 0.3s;
}

.container li:nth-child(1):hover~.top {
    height: 20%;
}

.container li:nth-child(2):hover~.top {
    height: 30%;
}

.container li:nth-child(3):hover~.top {
    height: 40%;
}

.container li:nth-child(4):hover~.top {
    height: 50%;
}

.container li:nth-child(5):hover~.top {
    height: 60%;
}

.container li:nth-child(6):hover~.top {
    height: 70%;
}