html {
    scroll-behavior: smooth;
}

body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
}

header {
    padding: 20px;
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    text-align: center;
    height: 60px;
    box-shadow: 0px 4px 8px rgba(0, 0, 0, 0.1);
}

a:visited {
    color: blue;
}

.logo {
    width: 220px;
}

nav ul {
    list-style-type: none;
    padding: 0;
    margin: 0;
    display: flex;
    justify-content: center;
}

nav ul li {
    margin: 0 10px;
}

nav > ul > li > a {
    color: #1a1a1a;
    text-decoration: none;
}

nav > ul > li > a:visited{
    color: #1a1a1a;
}

section {
    padding: 40px;
}

h1,
h2 {
    color: #333;
}

footer > ul > li > a {
    color: white !important;
}

section#services {
    margin-top: 40px;
    padding-top: 80px;
    padding-bottom: 80px;
    background: linear-gradient(135deg, #cecece 0%, #ffffff 100%);
    transform: skewY(-5deg);
    overflow: hidden;
}

section#services >* {
    transform: skewY(5deg);
}

.services-list {
    display: flex;
    gap: 16px;
    justify-content: center;
    flex-wrap: wrap;
}

section#contact {
    margin-top: 56px;
}

.flip-card {
    background-color: transparent;
    width: 300px;
    height: 350px;
    border: 1px solid #f1f1f1;
    perspective: 1000px;
}

.flip-card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    text-align: center;
    transition: transform 0.8s;
    transform-style: preserve-3d;
}

.flip-card:hover .flip-card-inner {
    transform: rotateY(180deg);
}

.flip-card-front,
.flip-card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    -webkit-backface-visibility: hidden;
    backface-visibility: hidden;
}

.flip-card-back > p {
    margin: 8px;
}

.flip-card-front {
    background-color: #bbb;
    display: flex;
    justify-content: center;
    align-items: center;
    color: white;
}

.flip-card-front > .icon {
    width: 200px;
    height: 200px;
    filter: invert(1);
    -webkit-filter: invert(1);
}

.flip-card-back {
    transform: rotateY(180deg);
}

.flip-card-back#heizung {
    background-image: linear-gradient(rgba(255, 255, 255, 0.5), rgba(255, 255, 255, 0.5)),
        url("../assets/img/services/anton-maksimov-heizung.jpg");
}

.flip-card-back#sanitär {
    background-image: linear-gradient(rgba(255, 255, 255, 0.5), rgba(255, 255, 255, 0.5)),
        url("../assets/img/services/photoholgic-bad.jpg");
}

.flip-card-back#lüftung {
    background-image: linear-gradient(rgba(255, 255, 255, 0.5), rgba(255, 255, 255, 0.5)),
        url("../assets/img/services/jan-kopankiewicz-lüftung.jpg");
}

.flip-card-back#wasserenthärtung {
    background-image: linear-gradient(rgba(255, 255, 255, 0.5), rgba(255, 255, 255, 0.5)),
        url("../assets/img/services/daniel-sinoca-wasser.jpg");
}

.flip-card-back#kundendienst {
    background-image: linear-gradient(rgba(255, 255, 255, 0.5), rgba(255, 255, 255, 0.5)),
        url("../assets/img/services/kenny-eliason-kundendienst.jpg");
}

footer {
    background-color: #333;
    color: #fff;
    text-align: center;
    padding: 20px;
}

footer ul {
    list-style-type: none;
    padding: 0;
    margin: 10px 0;
    display: flex;
    justify-content: center;
}

footer ul li {
    margin: 0 10px;
}

#back-to-top {
    background-color: #1a1a1a;
    color: white;
    z-index: 100;
    border-color: transparent;
    width: 40px;
    height: 40px;
    border-radius: 20px;
    -webkit-border-radius: 20px;
    -moz-border-radius: 20px;
    -ms-border-radius: 20px;
    -o-border-radius: 20px;
    position: fixed;
    bottom: 24px;
    right: 24px;
}

section#sources > a {
    color: black;
}