inst/reveal.js-5.1.0/plugin/chalkboard/style.css

div.palette, div.boardhandle {
  position: absolute;
/*
  height: 260px;
  margin: -130px 0 0 0px;
*/  
  top: 50%;
  transform: translateY(-50%);
  font-size: 24px;
  border-radius: 10px;
  border-top:    4px solid #222; 
  border-right:  4px solid #222; 
  border-bottom: 4px solid #222;
  background: black;
  transition: transform 0.3s;
}

div.palette  {
  left: -10px;
  padding-left:10px;
}

div.boardhandle {
  right: -10px;
  padding-right:10px;
}

div.palette > ul,
div.boardhandle > ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
}

div.palette > ul > li,
div.boardhandle > ul > li {
  margin: 10px;
}

@media print {
	div.palette, div.boardhandle { 
		display: none!important; 
	}
}