JSFiddle - React, Tailwind, and code Playground

by Richard Hunter

HTML

<div class="container">
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
</div>

CSS

body {
  display: flex;
}

.container {
  display: grid;
  grid-template-columns: repeat(3, auto);
  gap: 10px;
  margin: auto;
}

.box {
  background: red;
  height: 100px;
  width: 100px;
}

.box:nth-child(6n - 5),
.box:nth-child(6n - 4),
.box:nth-child(6n - 3) {
  border: solid 1px black;
  background: transparent;
}