main.css

body {
    padding: 0;
    margin: 0;
    line-height: 1.4em;
}

header {
    border-bottom: 1px solid lightgray;
    & a {
        text-decoration: none;
        color: green;
    }
    & h1 {
        margin-left: 40px;
        font-size: min(7vw, 2.5em);
    }
}

footer {
    border-top: 1px solid lightgray;
    display: flex;
    justify-content: center;
    padding-block: 20px;

    & ul {
        display: flex;
        gap: 20px;
        list-style-type: none;
        padding: 0;
        margin: 0;
    }
}

.claim {
    font-size: 1.5em;
    font-weight: normal;
    line-height: 1.4em;
    border-left: 4px solid green;
    padding-left: 20px;
}


body {
    font-family: sans-serif;
    display: flex;
    align-items: center;
    flex-direction: column;
}

header, footer {
    width: 100%;
}

section {
    width: min(80ch, 95%);
}