* {
    box-sizing: border-box;
}

body {
    margin: 0;
    color: #252525;
    font-family: Arial, Helvetica, sans-serif;
    background: #f7f7f3;
}

a {
    color: inherit;
}

.site-header {
    position: sticky;
    top: 0;
    z-index: 20;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
    padding: 18px clamp(16px, 4vw, 56px);
    background: #ffffff;
    border-bottom: 1px solid #dddddd;
}


.brand {
    display: flex;
    align-items: center;
    gap: 12px;
    color: #252525;
    text-decoration: none;
}

.site-footer {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-items: center;
    gap: 10px 18px;
    width: 100%;
    margin: 0 auto;
    padding: 20px clamp(16px, 4vw, 40px) 28px;
    text-align: center;
    color: #4c585b;
    font-size: 14px;
    border-top: 1px solid #d8d8d0;
}

.site-footer a {
    color: #005ea8;
    font-weight: 700;
    text-underline-offset: 2px;
}

.brand img {
    width: 172px;
    height: auto;
}

.site-header nav {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.site-header nav a {
    padding: 8px 12px;
    border-radius: 4px;
    text-decoration: none;
    background: #ece9df;
}

.site-header nav a.active {
    color: #ffffff;
    background: #2f6f73;
}

main {
    max-width: 1180px;
    margin: 0 auto;
    padding: 26px clamp(16px, 4vw, 40px) 56px;
}

.intro-section {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(390px, 460px);
    gap: clamp(24px, 5vw, 56px);
    align-items: start;
    padding: 18px 0 34px;
}

.intro-copy h1 {
    margin: 0 0 18px;
    font-size: 34px;
}

.intro-copy p {
    max-width: 720px;
    margin: 0 0 16px;
    font-size: 17px;
    line-height: 1.6;
}

.signature {
    margin-top: 22px;
    color: #4c585b;
}

.featured-book {
    display: grid;
    grid-template-columns: 140px minmax(220px, 1fr);
    gap: 18px;
    align-items: end;
    margin-top: 62px;
    color: #252525;
    text-decoration: none;
}

.featured-book:hover img,
.featured-book:focus-visible img {
    border-color: #7a8588;
}

.featured-book img {
    align-self: start;
    display: block;
    width: 100%;
    height: auto;
    object-fit: contain;
    border: 1px solid #aeb7ba;
}

.featured-book-copy {
    display: grid;
    gap: 8px;
    align-content: end;
    justify-items: start;
    min-width: 0;
}

.book-title {
    display: grid;
    gap: 2px;
    font-size: 20px;
    font-weight: 700;
}

.book-part {
    color: #4c585b;
}

.book-note {
    font-size: 15px;
    line-height: 1.45;
}

.book-link {
    margin-top: 4px;
    padding: 8px 12px;
    color: #252525;
    font-weight: 700;
    background: #f1c84c;
    border-radius: 4px;
}

.textbooks-section {
    padding: 14px 0 0;
}

.textbooks-image {
    display: block;
    width: 100%;
    height: auto;
    border-radius: 6px;
}

@media (max-width: 760px) {
    .site-header {
        align-items: flex-start;
        flex-direction: column;
    }

    .site-header nav a {
        padding: 7px 9px;
    }

    .intro-section {
        grid-template-columns: 1fr;
    }

    .intro-copy h1 {
        font-size: 30px;
    }

    .featured-book {
        grid-template-columns: 130px minmax(210px, 1fr);
        gap: 14px;
        max-width: 460px;
        margin-top: 0;
    }
}

@media (max-width: 460px) {
    .featured-book {
        grid-template-columns: 1fr;
        max-width: 360px;
        margin-top: 0;
    }

    .featured-book-copy {
        align-content: start;
    }
}