* {
  box-sizing: border-box;
}

.menu {
  float: left;
  width: 20%;
  text-align: center;
}

.menu a {
  background-color: #e5e5e5;
  padding: 8px;
  margin-top: 7px;
  display: block;
  width: 100%;
  color: black;
  font-weight: bold;
}

.index {
  width: 100%;
  text-align: left;
}

.index a {
  background-color: #FFFFFF;
  width: 100%;
  color: black;
}

.index a:hover {
  color: purple;
}

.main {
  float: left;
  width: 60%;
  margin-top: 7px;
  padding: 0 20px;
  color: black;
}

.main a {
  background-color: #FFFFFF;
  width: 100%;
  color: black;
}

.main a:hover {
  color: purple;
}

.right {
  background-color: #e5e5e5;
  float: left;
  width: 20%;
  padding: 15px;
  margin-top: 7px;
  text-align: center;
  vertical-align: top;
}

.right a {
 color: black;
}

@media only screen and (max-width: 620px) {
  /* For mobile phones: */
  .menu, .main, .right {
    width: 100%;
  }
}

#topBtn {
  display: none;
  position: fixed;
  bottom: 10px;
  right: 15px;
  z-index: 99;
  font-size: 18px;
  border: none;
  outline: none;
  background-color: darkGray;
  color: white;
  cursor: pointer;
  padding: 10px;
  border-radius: 4px;
}

#topBtn:hover {
  background-color: #555;
}

.downloadButton {
    background-color: #5c5959;
    color: white;
    padding: 4px 4px;
    border-radius: 4px;
    border: none;
    cursor: pointer;
  }

.video-container {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 aspect ratio */
    padding-top: 0;
    height: 0;
    overflow: hidden;
    width: 100%;
}

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