ใช้ sweetalert2 แล้วเวลากด sign in พวกตัว container มันเด้งขึ้นไปด้านบนแก้ยังไงครับ

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HTML CSS JavaScript การพัฒนา Web Application Web Browser

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อันนี้โค้ดทั้งหมดครับ
HTML
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Login</title>
    <link rel="stylesheet" href="style.css">
</head>
<body class="body">
    <div class="container">
        <h1>Asset Management System</h1>
        <div class="login-con">
            <p class="user">Username</p>
            <div class="input-box">
                <input type="text" class="username">
            </div>
            <p class="pass">Password</p>
            <div class="input-box">
                <input type="text" class="password">
            </div>
            <div class="btn">
                <button class="button">Sign in</button>
            </div>
        </div>
    </div>
    <script src="https://cdn.jsdelivr.net/npm/sweetalert2@11"></script>
    <script src="app.js"></script>
</body>
</html>

JS
const users = [
    { "id": 1, "username": "admin", "password": "1111", "role": 1 },
    { "id": 2, "username": "aaa", "password": "2222", "role": 2 },
    { "id": 3, "username": "bbb", "password": "333", "role": 2 }
    ];
    let body = document.querySelector('.body');
document.querySelector('.button').addEventListener('click', function checkUser() {
    const user = document.querySelector('.username').value;
    const pass = document.querySelector('.password').value;
    const checkUser = users.find(u => (u.username == user && u.password == pass));
    if (checkUser) {
        Swal.fire({
            icon: 'success',
            title: 'Success'
        });
    } else {
        Swal.fire({
            icon: 'error',
            title: 'Error',
            text: 'Login failed, try again!'
        });
    }
});

CSS
* {
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}
.body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
}
h1 {
    margin-bottom: 70px;
    font-size: 40px;
}
.login-con {
    border: 2px solid rgb(0, 102, 255);
    border-radius: 10px;
    height: 20rem;
    width: 90%;
    background: #fff;
    margin-left: 20px;
    box-shadow: 0 0 5px;
}
.user {
    font-size: 30px;
    font-weight: 300;
    margin: 20px 0 0 40px;
}
.input-box {
    display: flex;
    justify-content: center;
}
.input-box input {
    width: 80%;
    height: 3.5rem;
    margin: 10px 0 0 0;
    padding-left: 5px;
    font-size: 25px;
    align-items: center;
    border: none;
    border: 2px solid rgb(0, 0, 0, 0.1);
    border-radius: 5px;
}
.pass {
    font-size: 30px;
    font-weight: 300;
    margin: 10px 0 0 40px;
}
.button {
    width: 80%;
    height: 3rem;
    margin: 20px 0 0 40px;
    background-color: rgb(71, 135, 255);
    color: #fff;
    font-size: 20px;
    border: none;
    border-radius: 10px;
}
.button:hover {
    cursor: pointer;
    outline: 2px solid rgb(0, 0, 0, 1);
}