box-shadow (one side only)

.box-shadow::after {
  content: "";
  position: absolute;
  width: 100%;
  bottom: -1px;
  z-index: -1;
  box-shadow: 0 0 4px 1px rgba(0, 0, 0, 0.4);
}

.element {
  position: relative;
}

<div class="element box-shadow">
  <!-- content here -->
 </div>

.element::before {
    content: "";
    position: absolute;
    top: -18px; /* positions arrow on top of container */
    left: 50%; /* works with transform to center the arrow */
    transform: translateX(-50%);
    border: 10px solid; /* creates a 10px box */
/*  border-color: red green yellow black; */ 
    border-color: transparent transparent white transparent;
    /* the red/green etc used for testing, then swap to transparent version */
}

.underline {
    position: relative;
}

.underline::after {
    content: "";
    position: absolute;
    bottom: -15px;
    left: 0;
    width: 100%;
    height: 2px;
    background-color: #000;
}

Choices([@YouTubeIDs].AddToWatchList)

//HTML
<div class='dropdown'>
          <Link id='product' className='every' to='/products'>OUR PRODUCTS</Link>
           <div class='dropdown-content'>
            <Link to='autocadd'>AutoCadd</Link>
            <Link to='techset'>Techset</Link>
            <Link to='Endorse'>Endorse</Link>
           </div>
          </div>

//CSS

.dropdown{
    position: relative;
    display: inline-block;
}
.dropdown-content{
    display: none;
    position: absolute;
    background-color: #f1f1f1;
    min-width: 160px;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    z-index: 1;
}

.dropdown-content>*{
 color: black;
 padding: 12px 6px;
text-decoration: none;
 display: block;
}

.dropdown:hover .dropdown-content{
    display: block;
}
.dropdown-content>*:hover{
    background-color: #ddd;
}

document.addEventListener("DOMContentLoaded", function(){
// make it as accordion for smaller screens
if (window.innerWidth > 992) {

	document.querySelectorAll('.navbar .nav-item').forEach(function(everyitem){

		everyitem.addEventListener('mouseover', function(e){

			let el_link = this.querySelector('a[data-bs-toggle]');

			if(el_link != null){
				let nextEl = el_link.nextElementSibling;
				el_link.classList.add('show');
				nextEl.classList.add('show');
			}

		});
		everyitem.addEventListener('mouseleave', function(e){
			let el_link = this.querySelector('a[data-bs-toggle]');

			if(el_link != null){
				let nextEl = el_link.nextElementSibling;
				el_link.classList.remove('show');
				nextEl.classList.remove('show');
			}


		})
	});

}
// end if innerWidth
}); 
// DOMContentLoaded  end

<script>
  let items = document.querySelector(".header__inline-menu").querySelectorAll("details");
  console.log(items)
  items.forEach(item => {
    item.addEventListener("mouseover", () => {
      item.setAttribute("open", true);
      item.querySelector("ul").addEventListener("mouseleave", () => {
        item.removeAttribute("open");
      });
    item.addEventListener("mouseleave", () => {
      item.removeAttribute("open");
    });
  });
  
  });
</script>