body {
  font-family: Arial, sans-serif;
  text-align: center;
  padding-top: 10px;
  margin: 0px;
  padding: 0px;
  min-height: auto;
  flex: 1;
  background: linear-gradient(-45deg, #2d0036, #0d0d0d, #3a0c59, #000000);
  background-size: 400% 400%;
  animation: gradientShift 15s ease infinite;
  color: white;
}

header nav ul{
  list-style-type: none;
  background-color: hwb(0 57% 43% / 0.684);
  padding: 0px;
  margin: 0px;
  overflow: hidden;
}

header nav li{
  float: left;
}

header nav ul a{
  text-decoration: none;
  color: white;
  padding: 15px;
  display: block;
  text-align: center;
}

header nav ul a:hover{
  background-color: hsla(0, 0%, 46%, 0.89);
}

footer {
  margin-top: 50px;
  text-align: center;
  width: 100%;
  padding: 0px;
  background-color: white;
  color: #777;
  font-size: 16px;
} 

@keyframes gradientShift {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

button {
  padding: 10px 20px;
  margin: 10px;
  font-size: 16px;
  cursor: pointer;
  border: none;
  border-radius: 12px;
  background-color: #ffffff9a;
  color: #2d0036;
  transition: background-color 0.3s ease;
}

button:hover {
  background-color: #ffffff;
}

.visible {
  display: block;
  width: auto;
  height: 400px;
  margin: 20px auto;
  border-radius: 12px;
  box-shadow: 0 0 20px #8a2be2cc;
}

.invisible {
  display: none;
  width: auto;
  height: 400px;
  margin: 20px auto;
  border-radius: 12px;
  box-shadow: 0 0 20px #8a2be2cc;
}