Advanced button customization

Besides simply changing the button color, you can completely change its appearance – change the font, add borders, hower and click animations and other stuff that can be done with CSS. Foe example,

.uploadcare--widget__button_type_open {
  cursor: pointer;
  font-family: Arial, Helvetica, sans-serif;
  font-size: 24px;
  font-weight: bold;
  text-shadow: 0 -1px 1px rgba(0, 0, 0, 0.25);
  padding: 1px 14px;
  background-color: #e22092;
  background: linear-gradient(#e85eac, #e02a91);
  border-bottom: 1px solid rgba(0, 0, 0, 0.25);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.6);
  -webkit-transition: -webkit-transform 0.25s;
  -moz-transition: -moz-transform 0.25s;
  transition: transform 0.25s;
}

.uploadcare--widget__button_type_open:hover {
  background: linear-gradient(#e14296, #d71876);
  -webkit-transform: scale(1.05);
  -moz-transform: scale(1.05);
  transform: scale(1.05);
}

.uploadcare--widget__dragndrop-area {
  line-height: 3.4;
  margin-top: -1.8em;
}

See this live demo that shows how to make the widget button look completely different.