ribbon.css

.ribbon {
  position: fixed;
  overflow: hidden;
  left: 0;
  top: 0;
  z-index: 1000;
  width: 12em;
  height: 12em;
  font-size: 15px;
  text-decoration: none;
  text-indent: -1000px;
  pointer-events: none;
}

.ribbon:before,
.ribbon:after {
  position: absolute;
  display: block;
  width: 15.8em;
  height: 1.5em;

  top: 3em;
  left: -3em;

  -webkit-box-sizing: content-box;
  -moz-box-sizing: content-box;
  box-sizing: content-box;

  -webkit-transform: rotate(-45deg);
  -moz-transform: rotate(-45deg);
  -ms-transform: rotate(-45deg);
  -o-transform: rotate(-45deg);
  transform: rotate(-45deg);
}

.ribbon:before {
  content: "";
  padding: 0.4em 0;
  background-color: rgb(20, 120, 20);
  pointer-events: auto;
}

.ribbon:after {
  content: attr(title);

  color: white;
  font: 800 1em Helvetica, Arial, sans-serif;
  line-height: 1.5em;
  text-decoration: none;
  text-align: center;
  text-indent: 0;

  padding: 0.15em 0;
  margin: 0.15em 0;

  border-width: 0.08em 0;
  border-style: dotted;
  border-color: white;
}