番外編：行数が異なる画像の横並びの練習

CSS Gridで設定

<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="UTF-8">
<title>【コーディング練習】行数が異なる画像の横並びの練習</title>
<meta name="viewport" content="width=device-width">
<link rel="stylesheet" href="css/grid.css">
</head>
<body>
<div class="content">
<h2 class="content-title">PROJECT</h2>
<ul class="img-block">
  <li><img src="img/project1.jpg" alt=""></li>
  <li><img src="img/project2.jpg" alt=""></li>
  <li><img src="img/project3.jpg" alt=""></li>
  <li><img src="img/project4.jpg" alt=""></li>
  <li><img src="img/project5.jpg" alt=""></li>
  <li><img src="img/project6.jpg" alt=""></li>
  <li><img src="img/project7.jpg" alt=""></li>
  </ul>
</ul><!-- /.img-block -->
</div><!-- /.content -->
</body>
</html>

@charset "UTF-8";

/* ----------------------------------------
reset
---------------------------------------- */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
ul, li {
  list-style: none;
}
a {
  color: inherit;
  text-decoration: none;
  border: none;
}
img {
  max-width: 100%;
  vertical-align: bottom;
}


/* ----------------------------------------
layout
---------------------------------------- */
.content {
  margin-top: 100px;
  padding: 0 20px;
  }
.content-title {
  margin-bottom: 80px;
  font-size: 16px;
  font-weight: normal;
}
.img-block {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
}
  .img-block li:first-child {
    grid-column: 1 / 3;
    grid-row: 1 / 2;
  }

@media screen and (min-width: 900px) {
  .content {
    max-width: 1200px;
    margin: 100px auto 0;
  }
  .img-block {
    grid-template-columns: 40% 1fr 1fr 1fr;
    grid-template-rows: repeat(2, 1fr);
  }
  .img-block li:first-child {
    grid-column: 1 / 2;
    grid-row: 1 / 3;
  }
}