header, footer 
  { background: linear-gradient(#f0f56c, #afb50d);
  color: #0148FA;
  text-align: center;
  border-radius: 25px;
  border: 2px solid black;}
  nav ul li 
  {display:inline; 
  margin:5px;
  border-radius: 20px;
  border: 2px solid yellow;}
  .flex-container {    display: -webkit-flex;
    display: flex;
    width: 100%;
    background-color: yellow;
    border-radius: 20px}
  .flex-item {    text-align:left;
    line-height: 100px;
    font-weight: bold;
    background-color: #f4f799;
    width: 25%;
    height: 100px;
    margin: 10px;
    border-radius: 20px}
    section 
    {text-align: center}
  @keyframes example { 
      0% {background-color: red; left:0px; top:0px;}
      25% {background-color: yellow; left:200px; top:0px;} 
      50% {background-color: blue; left:200px; top:200px;} 
      75% {background-color: green; left:0px; top:200px;} 
      100% {background-color: red; left:0px; top:0px;} } 
  
  .iniz { width: 100px;
    height: 100px;
    text-align: center;
    background: YELLOW;
    -webkit-transition: width 1s;
    transition: width 1s;}
  div.iniz:hover {width: 1900px;}