CSS

body {
    margin: 0;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
}

.header {
    background-color: crimson;
    text-align: center;
    padding: 1px;
    color: white;
}

.topnav {
    overflow: hidden;
    background-color: black;
}

.topnav a {
    float: left;
    padding: 14px 16px;
    text-align: center;
    text-decoration: none;
    color: white;
    background-color: black;
    display: block;
}

.topnav a:hover {
    background-color: crimson;
    transition: ease-in-out .3s;
}

.row {
    display: flex;
}

.column1,
.column2,
.column3 {
    border: 2px solid crimson;
    float: left;
    text-align: center;
    width: 30%;
    padding: 20px;
    margin: 4px;
    background-color: crimson;
    border-radius: 10px;
    color: white;
}

.row::after {
    content: "";
    display: table;
    clear: both;

}

.container {
    text-align: center;
}

.button {
    padding: 15px 25px;
    font-size: 24px;
    text-align: center;
    cursor: pointer;
    outline: none;
    color: #fff;
    background-color: crimson;
    border: none;
    border-radius: 15px;
    box-shadow: 0 9px #666;
}

.button:hover {
    cursor: pointer;
}

.button:active {
    background-color: crimson;
    box-shadow: 0 5px black;
    transform: translateY(4px);
}

.footer {
    text-align: center;
    margin: 0;
    padding: 10px;
    background-color: black;
    color: white;
    margin-top: 30px;
}

@media screen and (max-width: 600px) {

    .column.side,
    .column.middle {
        width: 100%;
    }
}