JSFiddle - React, Tailwind, and code Playground

HTML

<div class="block">

  <div class="item"></div>
  <div class="item"></div>

</div>

SCSS

@import url('https://fonts.googleapis.com/css2?family=Neucha&display=swap');


* {
  box-sizing: inherit;
}

html {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: 'Neucha', cursive;
}
.block {
  display: flex;
  max-width: 400px;
  box-shadow: 0px 0px 0px 1px black;
}
.item {
  flex: 1;
  height: 100px;
  border: 1px solid red;
}