
부트 스트랩으로 따온걸 적용하면 가로로 적용이 되어야 하는데 세로로 적용이 됩니다

위에 처럼 세로로만 적용이 되어서 어느부분이 문제인지를 모르겠습니다
작성한 코드 및 에러 메세지
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>항해 10기 미니 프로젝트</title>
</head>
<link href="https://fonts.googleapis.com/css2?family=Jua&family=Nanum+Myeongjo:wght@400;700;800&family=Noto+Serif+KR:wght@200&display=swap"
rel="stylesheet">
<style>
* {
font-family: 'Noto Serif KR', serif;
}
.mypost {
color: white;
max-width: 100%;
height: 400px;
background-image: linear-gradient(0deg, rgba(0, 0, 0, 0.4), rgba(0, 0, 0, 0.4)), url("https://now.rememberapp.co.kr/wp-content/uploads/2020/05/%E1%84%82%E1%85%A6%E1%86%BA%E1%84%91%E1%85%B3%E1%86%AF%E1%84%85%E1%85%B5%E1%86%A8%E1%84%89%E1%85%B3.png");
background-size: cover;
background-position: center;
display: flex;
flex-direction: column;
justify-content: center;
align-items: center;
}
.mypost > button {
width: 200px;
height: 50px;
color: white;
background-color: transparent;
border-color: white;
border-radius: 20px;
border: 1px solid white;
}
.mypost > button:hover {
border: 2px solid white;
}
.mybtn {
width: 100px;
height: 50px;
color: black;
background-color: white;
border-radius: 10px;
margin-left: 150%;
}
</style>
<body>
<div class="mypost">
<div>
<button class="mybtn">로그인</button>
<h1>넷플릭스 인상깊은 작품</h1>
</div>
<button>작품 추천하기</button>
</div>
<div>
<div class="row row-cols-1 row-cols-md-3 g-4">
<div class="col">
<div class="card h-100">
<img src="..." class="card-img-top" alt="...">
<div class="card-body">
<h5 class="card-title">Card title</h5>
<p class="card-text">This is a longer card with supporting text below as a natural lead-in to
additional content. This content is a little bit longer.</p>
</div>
</div>
</div>
<div class="col">
<div class="card h-100">
<img src="..." class="card-img-top" alt="...">
<div class="card-body">
<h5 class="card-title">Card title</h5>
<p class="card-text">This is a short card.</p>
</div>
</div>
</div>
<div class="col">
<div class="card h-100">
<img src="..." class="card-img-top" alt="...">
<div class="card-body">
<h5 class="card-title">Card title</h5>
<p class="card-text">This is a longer card with supporting text below as a natural lead-in to
additional content.</p>
</div>
</div>
</div>
<div class="col">
<div class="card h-100">
<img src="..." class="card-img-top" alt="...">
<div class="card-body">
<h5 class="card-title">Card title</h5>
<p class="card-text">This is a longer card with supporting text below as a natural lead-in to
additional content. This content is a little bit longer.</p>
</div>
</div>
</div>
</div>
</div>
</body>
</html>
