How can I center a flex item both vertically and horizontally within its container?

<!-- BEGIN COPY / PASTE -->
    <style>
      .container {
        display: flex;
        justify-content: center;
        align-items: center;
        height: 200px; /* Example height */
        border: 1px solid #ccc; /* Optional: for visual reference */
      }
      .item {
        width: 50px;
        height: 50px;
        background-color: lightblue;
      }
    </style>

    <div class="container">
      <div class="item"></div>
    </div>
    <!-- END COPY / PASTE -->