html, body {
    height: 100%;
    margin: 0;
    padding: 0;
    overflow: hidden;
    background-color: #000; /* Czarne tło */
}

.fullscreen-bg {
    background: url('tardis.png') no-repeat center center fixed;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    height: 100%;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
    opacity: 0; /* Start z niewidoczności */
    animation: fadeIn ease 3s;
    animation-fill-mode: forwards; /* Pozostawienie obrazu po zakończeniu animacji */
}

@keyframes fadeIn {
    0% {opacity:0;}
    100% {opacity:1;}
}

/* Powtórzenie keyframes dla różnych przeglądarek */
@-moz-keyframes fadeIn { /* Firefox */
    0% {opacity:0;}
    100% {opacity:1;}
}

@-webkit-keyframes fadeIn { /* Chrome, Safari, Opera */
    0% {opacity:0;}
    100% {opacity:1;}
}

@-o-keyframes fadeIn { /* Opera */
    0% {opacity:0;}
    100% {opacity:1;}
}

@-ms-keyframes fadeIn { /* Internet Explorer */
    0% {opacity:0;}
    100% {opacity:1;}
}