<div class="flex-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>
.flex-container {
    display: flex;
    height: 600px;
    flex-wrap: wrap;
    background-color: #678888;
}
.flex-container > div {
    background-color: #f1f1f1;
    width: 100px;
    height:100px;
    margin: 10px;
    text-align: center;
    line-height: 75px;
    font-size: 30px;
}

External CSS

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External JavaScript

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