h1{
    text-align:center;
}
h2{
    text-align:center;
}
h3{
    text-align:center;
}
ul{
    margin-left:40%;
}
iframe{
    margin-left:30%;
}
body{
    background-color:lightgreen;
}
img {
    height: 300px;
    width: 40%;
    margin-left: 30%;
    margin-right: 30%;
}
p{
    margin-left:30%;
    margin-right:30%;
}
.code-snippet{
    width:100%;
    border:solid;
    border-radius:10px;
    background-color:lightgray;
}