body, html{
  margin:0;
  padding:0;
  box-sizing: border-box;
 background-color: lightsteelblue;
}

iframe {
  display: block;
  height: 500px;
  width: 100%;
}

h1{
 font-size: 60px;
 font-family: 'Courier New', Courier, monospace;
 font-weight: bold;
 color: steelblue;
 text-align: center;
}

h3{
  font-size: 24px;
  font-family: 'Courier New', Courier, monospace;
  font-style: italic;
  color: steelblue;
  text-align: center;
}

h4{
  font-family: 'Courier New', Courier, monospace;
  font-size: 24px;
  color: steelblue;
  margin-left: 35px;
}

ul{
font-family:Arial, Helvetica, sans-serif;
color: steelblue;
}

ol{
  font-family: 'Courier New', Courier, monospace;
  font-style: italic;
  font-size: 24px;
  color: steelblue;
}

li{
  margin-left: 25px;
  font-family: 'Courier New', Courier, monospace;
  font-style: italic;}

a{
  display:inline-block;
  margin: 25px 25px 25px 50px;
}

#btn{
  font-family: 'Courier New', Courier, monospace;
  color: steelblue;
}

#btn:hover{
  color: red;
}

@media (max-width: 768px) {
  /* your tablet styles here! */
iframe {height: 400px; width: 768px;}
h1 {text-align: center;}
h1{font-size: 55px;}
h3 {text-align: center;}
ol {font-size: 20px;}
}

@media (max-width: 425px) {
   /* your mobile styles here! */
   iframe{display:none;}
   ol {font-size: 18px;}
   a{margin-top: 5px;}
 
}