CSS Grid/CSS-grid-auto-fit-minmax.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Grid Auto fit & Minmax</title>
    <style>
      .container > div {
        display: flex;
        justify-content: center;
        align-items: center;
        font-size: 2em;
        color: #ffeead;
      }
      .container > div:nth-child(even) {
        color: floralwhite;
        background: forestgreen;
      }
      .container > div:nth-child(odd) {
        color: floralwhite;
        background: tomato;
      }
      /* Grid */
      .container {
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(100px,1fr));
        grid-template-rows: repeat(2, 100px);
        grid-auto-rows:100px ;
        grid-gap: 5px;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <div>1</div>
      <div>2</div>
      <div>3</div>
      <div>4</div>
      <div>5</div>
      <div>6</div>
      <div>7</div>
      <div>8</div>
      <div>9</div>
      <div>10</div>
      <div>11</div>
      <div>12</div>
    </div>
  </body>
</html>