.topnav {
    background-color: #333;
    overflow: hidden;
  }
  
  /* Style the links inside the navigation bar */
.topnav a {
    float: left;
    color:white;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
    font-size: 17px;
  }
  
  /* Change the color of links on hover */
.topnav a:hover {
    background-color: gray;
    color: black;
  }
  
  /* Add a color to the active/current link */
  
.topnav a.active {
    background-color: black;
    color: white;
  }

  body{
    background-image: url(m20.jpg);
    background-size: 100vh auto;
    color: white;
    font-family: Arial, Helvetica, sans-serif;
    line-height: 1.2;
    min-height: 100vh;
    min-width: auto;
    background-attachment: fixed;
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
  }

  a{
    color: white;
  }

.geocentric{
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 40vh;
  width: auto;
}

.geocentricexplain{
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: center;
}

.heliocentric{
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 40vh;
  width: auto;
}

.heliocentric{
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: center;
}

.keplersecondlaw{
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 40vh;
  width: auto;
}