style.css

#error {
    color: red;
}
#progress_bar {
    margin: 10px 0;
    padding: 3px;
    border: 1px solid #000;
    font-size: 14px;
    clear: both;
    opacity: 0;
    -moz-transition: opacity 1s linear;
    -o-transition: opacity 1s linear;
    -webkit-transition: opacity 1s linear;
}
#progress_bar.loading {
    opacity: 1.0;
}
#progress_bar .percent {
    background-color: #99ccff;
    height: auto;
    width: 0;
}

/*   Buttons   */
.button {
  border: none;
  border-radius: 5px;
  color: white;
  padding-top: 15px;
  padding-bottom: 15px;
  padding-right: 30px;
  padding-left: 30px;
  margin-right: 6px;
  text-align: center;
  text-decoration: none;
  display: inline-block;
  font-size: 24px;
  cursor: pointer;
}

#upload {
	width: 0.1px;
	height: 0.1px;
	opacity: 0;
	overflow: hidden;
	position: absolute;
	z-index: -1;
}

#upload + label {
	background-color: #4CAF50;
}
#upload:focus + label,
#upload + label:hover {
    background-color: #3E8E41;
}

#download {background-color: #4CAF50;}
#download:hover {background-color: #3E8E41;}

#cancel {background-color: #7c7f7c;}
#cancel:hover {background-color: #af504c;}
/*   End Buttons   */