<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>
<body>
  <main>
    <div class="card">1</div>
    <div class="card">2</div>
    <div class="card">3</div>
    <div class="card">4</div>
    <div class="card">5</div>
    <div class="card">6</div>
    <div class="card">7</div>
    <div class="card">8</div>
    <div class="card">9</div>
    <div class="card">10</div>
    <div class="card">11</div>
  </main>
</body>
</html>
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

main {
  display: grid;
  grid-gap: 2rem;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  grid-auto-rows: minmax(150px, 1fr);
  grid-auto-flow: dense;
  padding: 2rem;
}

.card {
  background-color: #770f0f;
  border: 3px solid white;
  border-radius: .66rem;
  
  /*Center number in cards*/
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.