grid-auto-flow dense Block Fitting

grid-auto-flow dense Block Fitting by Wes Bos

HTML

<link rel="stylesheet" href="https://cdn.rawgit.com/wesbos/css-grid/master/assets/style.css">
<div class="container">
  <div class="item item1">1</div>
  <div class="item item2">2</div>
  <div class="item item3">3</div>
  <div class="item item4">4</div>
  <div class="item item5">5</div>
  <div class="item item6">6</div>
  <div class="item item7">7</div>
  <div class="item item8">8</div>
  <div class="item item9">9</div>
  <div class="item item10">10</div>
  <div class="item item11">11</div>
  <div class="item item12">12</div>
  <div class="item item13">13</div>
  <div class="item item14">14</div>
  <div class="item item15">15</div>
  <div class="item item16">16</div>
  <div class="item item17">17</div>
  <div class="item item18">18</div>
  <div class="item item19">19</div>
  <div class="item item20">20</div>
  <div class="item item21">21</div>
  <div class="item item22">22</div>
  <div class="item item23">23</div>
  <div class="item item24">24</div>
  <div class="item item25">25</div>
  <div class="item item26">26</div>
  <div class="item item27">27</div>
  <div class="item item28">28</div>
  <div class="item item29">29</div>
  <div class="item item30">30</div>
  <div class="item item31">31</div>
  <div class="item item32">32</div>
  <div class="item item33">33</div>
  <div class="item item34">34</div>
  <div class="item item35">35</div>
  <div class="item item36">36</div>
  <div class="item item37">37</div>
  <div class="item item38">38</div>
  <div class="item item39">39</div>
  <div class="item item40">40</div>
  <div class="item item41">41</div>
  <div class="item item42">42</div>
  <div class="item item43">43</div>
  <div class="item item44">44</div>
  <div class="item item45">45</div>
  <div class="item item46">46</div>
  <div class="item item47">47</div>
  <div class="item item48">48</div>
  <div class="item item49">49</div>
  <div class="item item50">50</div>
  <div class="item item51">51</div>
  <div class="item item52">52</div>
  <div class="item...

CSS

.container {
  display: grid;
  grid-gap: 20px;
  grid-template-columns: repeat(10, 1fr);
  grid-auto-flow: dense;
}
.item:nth-child(6n) {
  background: cornflowerblue;
  grid-column: span 6;
}
.item:nth-child(8n) {
  background: tomato;
  grid-column: span 2;
}
.item:nth-child(9n) {
  grid-row: span 2;
}
.item18 {
  background: greenyellow !important;
  grid-column-end: -1 !important;
}