* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: Arial, sans-serif;
    line-height: 1.6;
    background-color: #f3f5f7;
    color: #24303b;
}

.site-header {
    padding: 32px 20px;
    text-align: center;
    background-color: #e4edf2;
    border-bottom: 1px solid #ccd8df;
}

h1,
h2,
h3 {
    margin-top: 0;
    line-height: 1.3;
}

h1 {
    margin-bottom: 12px;
    font-size: 32px;
}

h2 {
    margin-bottom: 16px;
    font-size: 24px;
}

h3 {
    margin-bottom: 12px;
    font-size: 20px;
}

p {
    margin-top: 0;
    margin-bottom: 12px;
}

a {
    color: #215d78;
}

.layout {
    display: flex;
    gap: 24px;
    max-width: 1200px;
    margin: 24px auto;
    padding: 0 20px;
}

.sidebar {
    flex: 0 0 210px;
    align-self: flex-start;
    padding: 16px;
    background-color: #ffffff;
    border-radius: 12px;
}

.main-nav ul {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin: 0;
    padding: 0;
    list-style: none;
}

.main-nav a {
    display: block;
    padding: 10px 12px;
    border-radius: 8px;
    text-decoration: none;
}

.main-nav a:hover,
.main-nav a:focus-visible {
    background-color: #e4edf2;
    color: #163f52;
}

.content {
    flex: 1;
    min-width: 0;
}

section {
    margin-bottom: 24px;
    padding: 24px;
    background-color: #ffffff;
    border-radius: 12px;
}

section ul,
section ol {
    padding-left: 24px;
}

.cards {
    display: flex;
    flex-wrap: wrap;
    gap: 20px;
}

.card {
    flex: 1 1 240px;
    min-width: 0;
    padding: 20px;
    background-color: #f7fafc;
    border: 1px solid #d6e0e6;
    border-radius: 12px;
    box-shadow: 0 3px 8px rgba(0, 0, 0, 0.06);
    overflow-wrap: anywhere;
}

table {
    width: 100%;
    table-layout: fixed;
    border-collapse: collapse;
}

th,
td {
    padding: 12px;
    border: 1px solid #ccd8df;
    text-align: left;
    vertical-align: top;
    overflow-wrap: anywhere;
}

th {
    background-color: #e4edf2;
}

img {
    max-width: 100%;
    height: auto;
}

@media (max-width: 768px) {
    .layout {
        flex-direction: column;
        margin: 16px auto;
        padding: 0 16px;
    }

    .sidebar {
        flex: none;
        width: 100%;
    }

    .site-header {
        padding: 24px 16px;
    }

    h1 {
        font-size: 26px;
    }

    section {
        padding: 16px;
    }

    .card {
        flex: 1 1 100%;
    }

    th,
    td {
        padding: 8px;
        font-size: 14px;
    }
}
.book-cover {
    display: block;
    width: 180px;
    max-width: 100%;
    height: auto;
    margin: 0 auto 16px;
    border-radius: 6px;
}