<ul>
    <li>
        <a href="#">
            <ion-icon name="home-outline"></ion-icon>
        </a>
    </li>
    <li>
        <a href="#">
            <ion-icon name="person-outline"></ion-icon>
        </a>
    </li>
    <li class="active">
        <a href="#">
            <ion-icon name="add-circle-outline"></ion-icon>
        </a>
    </li>
    <li>
        <a href="#">
            <ion-icon name="settings-outline"></ion-icon>
        </a>
    </li>
    <li>
        <a href="#">
            <ion-icon name="chatbubble-outline"></ion-icon>
        </a>
    </li>
    <div id="marker"></div>
</ul>

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: #1e2759;
}

ul {
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 10px;
    box-shadow: 0 5px 25px rgba(0, 0, 0, 0.25);
}

ul li {
    list-style: none;

}

ul li a {
    position: relative;
    color: #fff;
    text-decoration: none;
    display: inline-block;
    padding: 20px 30px;
    z-index: 1000;
    backdrop-filter: blur(15px);
}

ul li a ion-icon {
    font-size: 1.5em;
    pointer-events: none;
    opacity: 0.25;
    transition: 0.25s;
}

ul li.active a ion-icon {
    opacity: 1;
}

#marker {
    position: absolute;
    top: 0;
    transition: 0.5s;
    z-index: 1;
}

#marker::before {
    content: '';
    position: absolute;
    top: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 50px;
    height: 40px;
    border-radius: 8px;
    background: #5da6ff;
    box-shadow: 0 0 15px #5da6ff,
        0 0 30px #5da6ff,
        0 0 40px #5da6ff,
        0 0 60px #5da6ff
}

ul li:nth-child(1).active~#marker::before {
    background: #5da6ff;
    box-shadow: 0 0 15px #5da6ff,
        0 0 30px #5da6ff,
        0 0 40px #5da6ff,
        0 0 60px #5da6ff
}

ul li:nth-child(2).active~#marker::before {
    background: #ff0;
    box-shadow: 0 0 15px #ff0,
        0 0 30px #ff0,
        0 0 40px #ff0,
        0 0 60px #ff0
}

ul li:nth-child(3).active~#marker::before {
    background: #df2fff;
    box-shadow: 0 0 15px #df2fff,
        0 0 30px #df2fff,
        0 0 40px #df2fff,
        0 0 60px #df2fff
}

ul li:nth-child(4).active~#marker::before {
    background: #0f0;
    box-shadow: 0 0 15px #0f0,
        0 0 30px #0f0,
        0 0 40px #0f0,
        0 0 60px #0f0
}

ul li:nth-child(5).active~#marker::before {
    background: #ff308f;
    box-shadow: 0 0 15px #ff308f,
        0 0 30px #ff308f,
        0 0 40px #ff308f,
        0 0 60px #ff308f
}

let marker = document.querySelector('#marker');
let list = document.querySelectorAll('ul li');

function moveIndicator(e) {
    marker.style.left = e.offsetLeft + 'px';
    marker.style.width = e.offsetWidth + 'px';
}
list.forEach(link => {
    link.addEventListener('mousemove', (e) => {
        moveIndicator(e.target);
    })
})
function activeLink() {
    list.forEach((item) =>
        item.classList.remove('active'));
    this.classList.add('active');
}
list.forEach((item) =>
    item.addEventListener('mouseover', activeLink));