html{
    height: 100%;
}
body{
    margin: 0;
    padding: 0;
    font-family: sans-serif;
    background: rgb(36, 28, 64);
}
.login-box .user-box input.error{
    border-bottom: 2px solid red;
}
.login-box .user-box input.valid{
    border-bottom: 2px solid rgb(150, 234, 24);
}
.login-box{
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%);
    width: 400px;
    padding: 40px;
    background: rgba(0, 0, 0, 0.5);
    box-sizing: border-box;
    border-radius: 10px;
}
.login-box h2{
    color: white;
    margin: 0 0 30px 0;
    padding: 0;
    text-align: center;
}
.login-box .user-box{
    position: relative;
}
.login-box .user-box input{
    width: 100%;
    padding: 10px 0;
    font-size: 16px;
    color: white;
    margin-bottom: 30px;
    border: none;
    background: transparent;
    border-bottom: 2px solid white;
    outline: none;
}
.login-box .user-box label{
    position: absolute;
    color: white;
    top: 0;
    left: 0;
    padding: 10px 0;
    font-size: 16px;
    pointer-events: none;
    transition: 0.5s;
}
.login-box .user-box input:focus~label,
.login-box .user-box input:valid~label{
    top: -26px;
    color: cornflowerblue;
    font-size: 12px;
}
#btn{
    width: 100%;
    padding: 10px;
    background-color: blue;
    color: white;
    border: none;
    border-radius: 5px;
    outline: none;
}
#err,#err2{
    position: absolute;
    left: 0;
    top: 65%;
    color: red;
    font-size: 12px;
}

.user-box{
    margin-bottom: 5px;
}