JSFiddle - React, Tailwind, and code Playground

HTML

<grid-item>A</grid-item>
<grid-item>B</grid-item>
<grid-item>C</grid-item>
<grid-item>D</grid-item>
<grid-item>E</grid-item>
<grid-item>F</grid-item>
<grid-item>A</grid-item>
<grid-item>B</grid-item>
<grid-item>C</grid-item>
<grid-item>D</grid-item>
<grid-item>E</grid-item>
<grid-item>F</grid-item>
<grid-item><div class="ribbon-wrapper"><div class="ribbon">NEW</div></div>PRO</grid-item>
<grid-item>B</grid-item>
<grid-item>C</grid-item>
<grid-item>D</grid-item>
<grid-item>E</grid-item>
<grid-item>F</grid-item>
<grid-item>A</grid-item>
<grid-item>B</grid-item>
<grid-item>C</grid-item>
<grid-item>D</grid-item>
<grid-item>E</grid-item>
<grid-item>F</grid-item>

SCSS

body {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  grid-auto-rows: 1fr;
  grid-gap: 5px;
  height: 100vh;
  padding: 5px;
  margin: 0;
  box-sizing: border-box;
}

grid-item {
  background-color: lightgreen;
  display: flex;
  justify-content: center;
  align-items: center;
}

.ribbon-wrapper {
  width: 85px; // the length should be not in px I think!
  height: 88px; // the length should be not in px I think!
  overflow: hidden;
  //position: absolute; it doesn't work!
  position: relative;
  top: -3px;
  left: -3px;
  .ribbon {
    font: bold 15px sans-serif;
    color: #333;
    text-align: center;
    -webkit-transform: rotate(-45deg);
    -moz-transform:    rotate(-45deg);
    -ms-transform:     rotate(-45deg);
    -o-transform:      rotate(-45deg);
    position: relative;
    padding: 7px 0;
    top: 15px;
    left: -30px;
    width: 120px;
    background-color: #ebb134;
    color: #fff;
  }
}