body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  text-align: center;
}

footer {
  color: white;
  background-color: #333;
  padding: 20px;
  margin: auto;
}

a {
  color: black;
}

.header h1 {
  font-size: 300%;
  padding: 0;
}

.photo {
  max-width: 1000px;
  margin: auto;
  padding: 0;
}

.section {
  max-width: 1000px;
  margin: auto;
  padding: 10px;
}

.iframe-container {
    overflow: hidden;
    position: relative;
    width: 100%;
    margin: 5px auto;
}

.iframe-container::after {
    padding-top: 56.25%;
    display: block;
    content: '';
}

.iframe-container iframe {
  position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

.topnav {
  overflow: hidden;
  background-color: #333;
  position: -webkit-sticky;
  /* Safari */
  position: sticky;
  top: 0;
  padding: 10px;
  z-index: 1;
  }

.topnav a {
  float: center;
  display: inline;
  color: white;
  text-align: center;
  padding: 18px 16px;
  text-decoration: none;
  font-size: 18px;
  z-index: 1;
  }

.grid {
  display: grid;
  padding: 5px 0;
}

.g4 {
  grid-template-columns: 10% 35% 25% 30%;
}

.g5 {
  grid-template-columns: 8% 22% 25% 30% 15%;
}

.cell {
  background-color: #f3f3f3;
  padding: 5px;
}

.cell a {
  color: none;
}

.celltop {
  background-color: #333;
  padding: 5px;
  color: white;
}

.b {
  font-weight: bold;
}

@media screen and (max-width: 600px) {

  .topnav a:not(:first-child) {
    display: none;
    }

  .topnav a {float:none;}
}

@media screen and (max-width: 768px) {

  .grid {
    grid-template-columns: auto;
  }

  .grid .cell {
    text-align: center;
  }

  .grid .celltop {
    text-align: center;
  }
}