.login_form {
    color: #fff;
    background: #666666;
    width: 100%;
    max-width: 400px;
    margin: 40px auto;
    padding: 20px 10px;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.5);
}
form {
    padding: 0 10px;
}
input[type="text"], input[type="password"], input[type="submit"] {
    background: #222;
    color: #fff;
    font-size: 16px;
    width: 100%;
    box-sizing: border-box;
    padding: 10px;
    margin: 10px 0;
    border: 1px solid #444;
    border-radius: 4px;
}
@media (max-width: 500px) {
    .login_form {
        max-width: calc(100vw - 50px);
        margin: 20px auto; /* Keep 'auto' for horizontal centering, reduce top/bottom */
        padding: 0.5em;
    }
}
@media (max-width: 400px) {
    h1 {
        font-size: 2em;
    }
    h2 {
        font-size: 1.3em;
    }
    input[type="text"], input[type="password"], input[type="submit"] {
        font-size: 14px;
        padding: 8px;
    }
}