body {
  font-family: "Open Sans", sans-serif;
  background-color: #f4f4f4;
  color: #333;
  margin: 0;
  font-size: large;
}

header {
  background-color: #007bff;
  color: white;
  text-align: center;
  padding: 3vh 0;
}

h1 {
  margin: 0;
  font-size: 3rem;
  text-shadow: 2px 2px rgba(0, 0, 0, 0.623);
}
h4 {
  margin-top: -0.7vh;
}
.themen {
  text-align: center;
  font-size: 3.5vh;
  text-shadow: none;
}

nav {
  background-color: #333;
  color: white;
  padding: 1.5vh;
}

nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  text-align: center;
}

nav ul li {
  display: inline;
  margin-right: 2vh;
}

nav ul li a {
  color: white;
  text-decoration: none;
  font-size: 1.1rem;
}

nav ul li a:hover {
  text-decoration: underline;
}

section {
  padding: 2vh;
  margin: 2vh 30vh;
  background-color: white;
  box-shadow: 0 0 1vh rgba(0, 0, 0, 0.1);
}

section h2 {
  color: #007bff;
}

section h3 {
  color: #333;
}
.topic {
  border: 0.2svh rgba(204, 204, 204, 0.705) solid;
  box-shadow: 0 0 1vh rgba(0, 0, 0, 0.1);
  border-radius: 0.6svh;
  color: #007bff;
  float: left;
  margin: 3vh 1vh;
  text-align: center;
  background-color: #eeeeee;
  padding: 2vh 3vh;
  justify-content: center;
}
div a {
  text-decoration: none;
  color: #007bff;
}
div a:visited {
  text-decoration: none;
  color: #007bff;
}

#herleitung {
  padding-bottom: 11vh;
}

.topic:hover {
  cursor: pointer;
  color: #007bffd8;
  background-color: #ebebebb6;
}

footer {
  background-color: #333;
  color: white;
  text-align: center;
  padding: 1.4vh 0;
  position: relative;
  width: 100%;
  bottom: 0;
}
img {
  max-width: 50vh;
  max-height: 30vh;
}
.zurückBtn {
  left: 2vh;
  top: 2vh;
  padding: 3vh 3vh;
  border: 0.3vh solid rgb(0, 0, 0);
  border-radius: 6px;
  background-color: #ffffffd3;
  color: #ffffff;
  font-size: 1.4em;
  cursor: pointer;
  transition: all 0.4s ease;
  outline: none;
  position: fixed;
  overflow: hidden;
  font-weight: bold;
  float: left;
}
.zurückBtn::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: radial-gradient(
    circle,
    rgba(255, 255, 255, 0.25) 0%,
    rgba(85, 95, 238, 0) 70%
  );
  transform: scale(0);
  transition: transform 0.5s ease;
}

.zurückBtn:hover::after {
  transform: scale(4);
}
.zurückBtn:hover {
  border-color: #d3d3d3;
  background: #e2e2e2;
}

.sign {
  width: 100%;
  transition-duration: 0.3s;
  display: flex;
  align-items: center;
  justify-content: center;
}
.sign svg {
  width: 17px;
}
.sign svg path {
  fill: #007bff;
}

.mainLinks {
  padding: 0.5vh 1vh;
  border-radius: 5px;
  transition: all 0.3s ease;
}

.mainLinks:hover {
  background-color: #535353;
}