How can I center a div both vertically and horizontally using flexbox?

<!-- BEGIN COPY / PASTE -->
    <style>
      .container {
        display: flex;
        justify-content: center; /* Centers horizontally */
        align-items: center;    /* Centers vertically */
        height: 100vh;          /* Full viewport height for vertical centering */
      }
      .centered-div {
        width: 200px;
        height: 100px;
        background-color: lightblue;
      }
    </style>

    <div class="container">
      <div class="centered-div">
        Centered Content
      </div>
    </div>
    <!-- END COPY / PASTE -->