.btn-file {
  position: relative;
  overflow: hidden;
  vertical-align: middle; }

.btn-file > input {
  position: absolute;
  top: 0;
  right: 0;
  width: 100%;
  height: 100%;
  margin: 0;
  font-size: 23px;
  cursor: pointer;
  filter: alpha(opacity=0);
  opacity: 0;
  direction: ltr; }

.file-drop-zone {
  height: 120px;
  border: dotted 1px lightgray; }

.file-drop-over {
  border: dotted 1px green;
  background-color: #b3e5fc; }