CSS file extension

file_ext.css.scss

// usage:
// .file-extension
//   %span TXT

body {
  background: #f0f0f0;
  padding: 2em;
}

.file-extension {
  $color: red;
  $fold: 15px;

  width: 70px;
  height: 100px;
  background: linear-gradient(-135deg, transparent 0%, transparent $fold * 1.4, $color $fold * 1.4 + 1px, $color 100%);
  position: relative;

  &:after {
    content: "";
    display: block;
    position: absolute;
    width: 0px;
    height: 0px;
    border: $fold solid;
    border-color: transparent transparent rgba(white, .6) rgba(white, .6);
    right: 0;
    top: 0;
  }

  &:before {
    content: "";
    display: block;
    position: absolute;
    width: 0px;
    height: 0px;
    border: $fold solid blue;
    border-color: darken($color, 15%) darken($color, 15%) transparent transparent;
    right: 0;
    top: $fold * 2;
  }

  span {
    background: darken($color, 15%);
    color: white;
    text-transform: capitalize;
    position: absolute;
    bottom: 5px;
    left: -5px;
    right: 5px;
    padding: 5px 10px;
    font-size: 16px;
  }
}