:root {
    --bg-color: #fcfcfc;
    --text-color: #1a1a1a;
    --card-bg: #ffffff;
    --secondary-text: #666666;
    --accent-color: #e0e0e0;
    --shadow-color: rgba(0, 0, 0, 0.04);

    --font-main: 'Inter', system-ui, -apple-system, sans-serif;

    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 2rem;
    --spacing-xl: 4rem;

    --container-width: 1200px;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: var(--font-main);
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}

main {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: var(--spacing-xl) var(--spacing-md);
}

main > header {
    margin-bottom: var(--spacing-xl);
    text-align: center;
}

h1 {
    font-weight: 600;
    font-size: 2rem;
    letter-spacing: -0.02em;
}

.section-nav {
    margin-top: var(--spacing-sm);
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--spacing-sm);
    font-size: 0.9rem;
}

.section-nav a {
    color: var(--secondary-text);
    text-decoration: none;
    padding: 0.2rem 0.6rem;
    border-radius: 999px;
    border: 1px solid var(--accent-color);
    transition: color 0.2s ease, border-color 0.2s ease, background-color 0.2s ease;
}

.section-nav a:hover,
.section-nav a:focus-visible {
    color: var(--text-color);
    background: var(--card-bg);
    border-color: var(--secondary-text);
}

.books-sections {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xl);
}

.books-section {
    width: 100%;
}

.section-header {
    margin-bottom: var(--spacing-md);
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    gap: var(--spacing-sm);
}

.section-title {
    font-size: 1.25rem;
    font-weight: 600;
    letter-spacing: -0.01em;
}

.section-count {
    font-size: 0.875rem;
    color: var(--secondary-text);
    white-space: nowrap;
}

/* Grid Layout */
.books-grid {
    display: grid;
    grid-template-columns: repeat(1, 1fr);
    gap: var(--spacing-lg);
    width: 100%;
}

@media (min-width: 600px) {
    .books-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (min-width: 900px) {
    .books-grid {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (min-width: 1100px) {
    .books-grid {
        grid-template-columns: repeat(4, 1fr);
    }
}

/* Book Card */
.book-card {
    background: var(--card-bg);
    border: 1px solid var(--accent-color);
    border-radius: 8px;
    padding: var(--spacing-md);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    display: flex;
    flex-direction: column;
}

.book-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px var(--shadow-color);
}

.book-cover {
    width: 100%;
    aspect-ratio: 2/3;
    object-fit: cover;
    background-color: var(--accent-color);
    border-radius: 4px;
    margin-bottom: var(--spacing-md);
    box-shadow: 0 2px 4px var(--shadow-color);
}

.book-title {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    line-height: 1.3;
}

.book-meta {
    font-size: 0.875rem;
    color: var(--secondary-text);
    margin-top: auto;
    /* Pushes meta to bottom if title is short */
}

.book-meta p {
    margin-top: var(--spacing-xs);
}

.loading,
.error {
    text-align: center;
    grid-column: 1 / -1;
    color: var(--secondary-text);
    padding: var(--spacing-xl);
}