JSFiddle - React, Tailwind, and code Playground

HTML

<div id="login_box">
    <form name="login_page" id="login_page" method="post">
        <input type="text" name="username" placeholder="Username" autofocus required="required" />
        <br />
        <input type="password" name="password" placeholder="Password" required="required" />
        <br />
        <div id="login_page_checkbox">
            <label class="checkbox">
                <input type="checkbox" name="rememberme" value="1">Remember me</label>
        </div>
        <br />
        <input type="submit" name="login_submit" value="Log In" />
    </form>
</div>

CSS

html, body {
    width: 100%;
}
#login_page {
    top: 0;
    margin-top: 50px;
    margin-left: 0;
    position: static;
}
#login_box {
    width: 100%;
}
input[type="text"], input[type="password"] {
    width: calc(100% - 30px) !important;
    margin: 5px !important;
}
#login_page input[type="submit"] {
    width: 97% !important;
    margin: 5px;
}