header {
  background-color: #f1f1f1;
  padding: 20px;
  text-align: center;
  font-size: 25px;
  color: black; }




body {
   background-color: #fff;
  background-image:
    linear-gradient(
      45deg,
      #000 25%,
      transparent 25%,
      transparent 75%,
      #000 75%,
      #000
    ),
    linear-gradient(
      -45deg,
      #000 25%,
      transparent 25%,
      transparent 75%,
      #000 75%,
      #000
    );
  background-size: 80px 80px;
  background-repeat: repeat;
}


.tab {
  overflow: hidden;
  border: 1px solid #ccc;
  background-color: #f1f1f1;
  padding: 10px;
}

.tab button {
  background-color: inherit;
  float: left;
  border: none;
  outline: none;
  cursor: pointer;
  padding: 14px 16px;
  transition: 0.3s;
}

.tab button:hover {
  background-color: #ddd;
}


.tab button.active {
  background-color: #ccc;
}


.tabcontent {
  display: none;
  background-color: #f1f1f1;
  padding: 6px 12px;
  border: 1px solid #ccc;
  border-top: none;
}
.tabcontent {
  animation: fadeEffect 0.5s; 
}

@keyframes fadeEffect {
  from {opacity: 0;}
  to {opacity: 1;}
}