html { 
    background-color: #000;
    background: url(lab.gif) no-repeat center center fixed;  
    background-size: cover;
    font-size: 1.5em;
    font-family: 'Vazirmatn', sans-serif;
    direction: rtl;
    text-align: center;
}

h1 {
    font-size: 1.5em;
    font-weight: bold;
    color: white;
}