* {
    font-family: "Trebuchet MS", sans-serif;
    box-sizing: border-box;
    #margin: 0;
    #padding: 0;
}
#main {
    display: flex;
}
#sections {
    display: flex;
    flex-direction: column;
    width: 60%;
}
#side-block {
    background: #C5CAE9;
    width: 40%;
    height: 600px;
    overflow: auto;
}
section {
    width: 100%;
    height: 300px;
}
#section-1 {
    background: #9FA8DA;
}
#section-2 {
    background: #7986CB;
}
footer {
    background: #283593;
    color: white;
    padding: 20px;
}
.opona {
    background: #9FA8DA;
    margin: 40px;
    border: 2px dotted #283593;
    border-radius: 30px;
}
img {
    padding: 20px;
    float: left;
}
h2 {
    text-align: center;
    margin: 0;
    padding: 15px;
}
h3 {
    background: #7986CB;
    color: white;
    font-size: 140%;
}
#section > h3 {
    display: inline;
}