style.css

.container {
  position:relative;
  width: 100%;
  height: 100%;
  overflow: clip;
}

.box {
  position: absolute;
  top: 0px;
  left: 0px;
  transform-origin: 0 0;
  -webkit-transform-origin: 0 0;
  -moz-transform-origin: 0 0;
  -o-transform-origin: 0 0;
}

.corner {
	display: none;
	width: 20px;
	height: 20px;
	position: absolute;
	top: 0px; left: 0px;
}

.corner::before {
	content: '';
	display: block;
	width: 20px;
	height: 20px;
	position: absolute;
	top: -20px; left: -9px;
	border-bottom: 2px solid black;
}

.corner::after {
	content: '';
	display: block;
	width: 20px;
	height: 20px;
	position: absolute;
	top: -9px; left: 0px;
	border-left: 2px solid black;
}


.overlay{
    position: fixed;
    top:0; right:0; bottom:0; left:0;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: 1000;
}

.fenetre_popup {
	display: none;
    background: #fff;
    padding: 20px;
    border: 20px solid #ddd;
    position: relative;
    margin: 10% auto;
    width: 40%;
    box-shadow: 0px 0px 20px #000;
    border-radius: 10px;
	text-align: center;
}

input {
	margin: 5px;
}

p {
	color: grey;
	font-size: 1.3em;
}

#textarea {
	overflow-y:hidden;
}

.modif {
	display: none;
}