JSFiddle - React, Tailwind, and code Playground

HTML

<h1>The system is down for maintenance.</h1>
<h3>Click the page to activate, then use backdoor key. [Ctrl+Space]</h3>
<div id="loginbox">
    <div>User
        <input type="text" />
    </div>
    <div>Password
        <input type="password" />
    </div>
    <input type="submit" />
</div>

JavaScript

/* Toggle Login */

function hideLogin(isHidden) {
    if (isHidden) {
        document.getElementById('loginbox').style.display = "none";
    } else {
        document.getElementById('loginbox').style.display = "block";
    }
}

/* define a handler */
function doc_keyUp(e) {
    /* http://www.javascripter.net/faq/keycodes.htm */
    if (e.ctrlKey && e.keyCode == 32) {
        hideLogin(false);
    } /* Ctrl+Space */
}

/* register the handler */
document.addEventListener('keyup', doc_keyUp, false);

hideLogin(true);