Widget:Details

<style> details div {

   border-left: 2px solid #000;
   border-right: 2px solid #000;
   border-bottom: 2px solid #000;
   padding: 1.5em;

}

details div > * + * {

   margin-top: 1.5em;

}

details + details {

   margin-top: .5rem;

}

summary {

   list-style: none;

}

summary::-webkit-details-marker {

   display: none;

}

summary {

   border: 2px solid #000;
   padding: .75em 1em;
   cursor: pointer;
   position: relative;
   padding-left: calc(1.75rem + .75rem + .75rem);

}

summary:before {

   position: absolute;
   top: 50%;
   transform: translateY(-50%);
   left: .75rem;
   content: "↓";
   width: 1.75rem;
   height: 1.75rem;
   background-color: #000;
   color: #FFF;
   display: inline-flex;
   justify-content: center;
   align-items: center;
   flex-shrink: 0;

}

details[open] summary {

   background-color: #eee;

}

details[open] summary:before {

   content: "+";

}

summary:hover {

   background-color: #eee;

} </style> <details open>

 <summary></summary>

</details>