oliverbooth.dev/src/scss/ribbon.scss

.ribbon {
  width: 150px;
  height: 150px;
  overflow: hidden;
  position: absolute;

  &::before, &::after {
    position: absolute;
    z-index: -1;
    content: '';
    display: block;
  }

  span {
    position: absolute;
    display: block;
    width: 225px;
    padding: 15px 0;
    box-shadow: 0 5px 10px rgba(0, 0, 0, .1);
    font: 700 18px/1 'Lato', sans-serif;
    text-shadow: 0 1px 1px rgba(0, 0, 0, .2);
    text-transform: uppercase;
    text-align: center;
  }

  &.ribbon-top-left {
    top: -10px;
    left: -10px;

    &::before, &::after {
      border-top-color: transparent;
      border-left-color: transparent;
    }

    &::before {
      top: 0;
      right: 0;
    }

    &::after {
      bottom: 0;
      left: 0;
    }

    span {
      right: -25px;
      top: 30px;
      transform: rotate(-45deg);
    }
  }

  &.ribbon-top-right {
    top: -10px;
    right: -10px;

    &::before, &::after {
      border-top-color: transparent;
      border-right-color: transparent;
    }

    &::before {
      top: 0;
      left: 0;
    }

    &::after {
      bottom: 0;
      right: 0;
    }

    span {
      left: -25px;
      top: 30px;
      transform: rotate(45deg);
    }
  }

  &.ribbon-bottom-left {
    bottom: -10px;
    left: -10px;

    &::before, &::after {
      border-bottom-color: transparent;
      border-left-color: transparent;
    }

    &::before {
      bottom: 0;
      right: 0;
    }

    &::after {
      top: 0;
      left: 0;
    }

    span {
      right: -25px;
      bottom: 30px;
      transform: rotate(225deg);
    }
  }

  &.ribbon-bottom-right {
    bottom: -10px;
    right: -10px;

    &::before, &::after {
      border-bottom-color: transparent;
      border-right-color: transparent;
    }

    &::before {
      bottom: 0;
      left: 0;
    }

    &::after {
      top: 0;
      right: 0;
    }

    span {
      left: -25px;
      bottom: 30px;
      transform: rotate(-225deg);
    }
  }

  &.red {
    $bg: #db3434;
    $fg: #fff;

    &::before, &::after {
      border: 5px solid darken($bg, 20%);
    }

    span {
      background-color: $bg;
      color: $fg;
    }
  }

  &.green {
    $bg: #34db34;
    $fg: #fff;

    &::before, &::after {
      border: 5px solid darken($bg, 20%);
    }

    span {
      background-color: $bg;
      color: $fg;
    }
  }

  &.blue {
    $bg: #3498db;
    $fg: #fff;

    &::before, &::after {
      border: 5px solid darken($bg, 20%);
    }

    span {
      background-color: $bg;
      color: $fg;
    }
  }
}

.project-card .ribbon {
  transform: scale(75%);
  left: -26px;
  top: -26px;
}