//slide down
.btn:checked ~ .box {
clip-path: polygon(0 0, 100% 0, 100% 100%, 0% 100%);
}
.box {
width: 350px;
margin-top: 2em;
position: absolute;
overflow: hidden;
border: 1px solid rgba(0, 0, 0, 0.137);
transition: all 0.4s;
clip-path: polygon(0 0, 100% 0, 100% 0, 0 0);
box-shadow: 0px 2rem 10px black;
}
//https://www.w3schools.com/howto/howto_js_slideshow.asp