:root {
    --pico-font-family: "Segoe UI", "Helvetica Neue", Arial, sans-serif;
    --pico-background-color: #f4f1ea;
    --pico-card-background-color: #fffdfa;
    --pico-card-border-color: rgba(53, 56, 52, 0.12);
    --pico-muted-border-color: rgba(53, 56, 52, 0.12);
    --pico-color: #22261f;
    --pico-muted-color: #5f665c;
    --pico-primary: #2f5a4f;
    --pico-primary-hover: #274c43;
    --pico-primary-focus: rgba(47, 90, 79, 0.2);
    --pico-secondary: #d9d2c5;
    --pico-secondary-hover: #cbc2b2;
    --pico-secondary-focus: rgba(95, 102, 92, 0.16);
    --pico-contrast: #7a3e2f;
    --pico-contrast-hover: #653325;
    --pico-form-element-background-color: #fffdfa;
    --pico-form-element-border-color: rgba(53, 56, 52, 0.18);
    --pico-form-element-color: #22261f;
    --site-nav-background: rgba(255, 253, 250, 0.82);
    --site-nav-border: rgba(53, 56, 52, 0.08);
    --site-shadow: rgba(46, 42, 35, 0.06);
    --site-badge-available-bg: rgba(47, 90, 79, 0.12);
    --site-badge-available-color: #1f5b43;
    --site-badge-unavailable-bg: rgba(122, 62, 47, 0.12);
    --site-badge-unavailable-color: #8a2f1d;
    --site-category-pill-bg: rgba(95, 102, 92, 0.1);
    --site-category-pill-color: #455046;
    --site-invalid-bg: rgba(122, 62, 47, 0.06);
    --site-invalid-border: rgba(122, 62, 47, 0.28);
    --site-invalid-color: #5d2d22;
}

@media (prefers-color-scheme: dark) {
    :root {
        --pico-background-color: #111512;
        --pico-card-background-color: #1a211d;
        --pico-card-border-color: rgba(227, 232, 223, 0.1);
        --pico-muted-border-color: rgba(227, 232, 223, 0.1);
        --pico-color: #edf2ea;
        --pico-muted-color: #a7b1a4;
        --pico-primary: #7eb09a;
        --pico-primary-hover: #95c2ae;
        --pico-primary-focus: rgba(126, 176, 154, 0.22);
        --pico-secondary: #2b342e;
        --pico-secondary-hover: #364139;
        --pico-secondary-focus: rgba(167, 177, 164, 0.18);
        --pico-contrast: #d27d68;
        --pico-contrast-hover: #e08b76;
        --pico-form-element-background-color: #141a17;
        --pico-form-element-border-color: rgba(227, 232, 223, 0.12);
        --pico-form-element-color: #edf2ea;
        --site-nav-background: rgba(26, 33, 29, 0.88);
        --site-nav-border: rgba(227, 232, 223, 0.08);
        --site-shadow: rgba(0, 0, 0, 0.35);
        --site-badge-available-bg: rgba(126, 176, 154, 0.16);
        --site-badge-available-color: #9fd3bb;
        --site-badge-unavailable-bg: rgba(210, 125, 104, 0.16);
        --site-badge-unavailable-color: #f0a18f;
        --site-category-pill-bg: rgba(167, 177, 164, 0.14);
        --site-category-pill-color: #d6ded2;
        --site-invalid-bg: rgba(210, 125, 104, 0.12);
        --site-invalid-border: rgba(210, 125, 104, 0.28);
        --site-invalid-color: #ffcabd;
    }
}

body {
    background:
        radial-gradient(circle at top left, rgba(255, 255, 255, 0.85), transparent 32%),
        linear-gradient(180deg, #f7f4ee 0%, #f1ede5 100%);
    min-height: 100vh;
}

@media (prefers-color-scheme: dark) {
    body {
        background:
            radial-gradient(circle at top left, rgba(126, 176, 154, 0.12), transparent 25%),
            linear-gradient(180deg, #111512 0%, #161c18 100%);
    }
}

main.container {
    padding-top: 2rem;
    padding-bottom: 3rem;
}

.container > header:first-child,
main > article > header:first-child {
    margin-bottom: 1.5rem;
}

nav {
    background: var(--site-nav-background);
    border: 1px solid var(--site-nav-border);
    border-radius: 1rem;
    padding: 0.85rem 1.1rem;
    margin-top: 1rem;
    backdrop-filter: blur(10px);
    box-shadow: 0 16px 40px var(--site-shadow);
}

nav ul {
    align-items: center;
    flex-wrap: wrap;
}

nav a {
    font-weight: 500;
    text-decoration: none;
}

article {
    box-shadow: 0 18px 50px var(--site-shadow);
}

.grid {
    align-items: start;
    grid-template-columns: repeat(4, minmax(0, 1fr));
}

.grid > article {
    height: 100%;
}

img {
    border-radius: 0.75rem;
}

.book-title {
    font-size: 1.2rem;
    line-height: 1.3;
}

footer.container {
    padding-bottom: 2rem;
}

footer.container small {
    display: block;
    text-align: center;
    color: var(--pico-muted-color);
}

small {
    color: var(--pico-muted-color);
}

.availability-badge {
    display: inline-flex;
    align-items: center;
    padding: 0.2rem 0.65rem;
    border-radius: 999px;
    font-weight: 600;
    font-size: 0.78rem;
    letter-spacing: 0.01em;
    margin-top: 0.35rem;
}

.availability-badge.is-available {
    background: var(--site-badge-available-bg);
    color: var(--site-badge-available-color);
}

.availability-badge.is-unavailable {
    background: var(--site-badge-unavailable-bg);
    color: var(--site-badge-unavailable-color);
}

.category-list {
    display: flex;
    flex-wrap: wrap;
    gap: 0.45rem;
    margin: 0.9rem 0 1rem;
}

.category-pill {
    display: inline-flex;
    align-items: center;
    padding: 0.22rem 0.7rem;
    border-radius: 999px;
    background: var(--site-category-pill-bg);
    color: var(--site-category-pill-color);
    font-size: 0.78rem;
    font-weight: 600;
    letter-spacing: 0.01em;
}

[aria-invalid="true"],
article[aria-invalid="true"] {
    border-color: var(--site-invalid-border);
}

article[aria-invalid="true"] {
    background: var(--site-invalid-bg);
    color: var(--site-invalid-color);
}

@media (prefers-color-scheme: dark) {
    nav a,
    nav strong,
    .book-title,
    article header,
    article strong,
    h1,
    h2,
    h3 {
        color: var(--pico-color);
    }

    article img {
        box-shadow: 0 10px 30px rgba(0, 0, 0, 0.28);
    }

    input,
    select,
    textarea {
        box-shadow: none;
    }

    small {
        color: var(--pico-muted-color);
    }
}

article p:last-child {
    margin-bottom: 0;
}

article footer {
    display: flex;
    gap: 0.75rem;
    flex-wrap: wrap;
    padding-top: 0.5rem;
}

article footer a[role="button"] {
    margin-bottom: 0;
}

select[multiple] {
    min-height: 12rem;
}

@media (max-width: 768px) {
    nav {
        padding: 0.9rem;
    }

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

    article footer {
        flex-direction: column;
    }
}

@media (max-width: 1200px) {
    .grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}