/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #000000;
    --primary-hover: #333333;
    --text-color: #1a1a1a;
    --text-light: #666666;
    --bg-color: #ffffff;
    --bg-light: #fafafa;
    --border-color: #e5e5e5;
    --max-width: 1000px;
    --spacing: 2rem;
    --border-radius: 4px;
    --transition: all 0.2s ease;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.7;
    color: var(--text-color);
    background-color: var(--bg-color);
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Header and Navigation */
header {
    background-color: var(--bg-color);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(10px);
    background-color: rgba(255, 255, 255, 0.9);
}

.nav-container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 1.5rem var(--spacing);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
}

.logo {
    font-size: 1.1rem;
    font-weight: 500;
    color: var(--text-color);
    letter-spacing: -0.02em;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2.5rem;
    flex-wrap: wrap;
}

.nav-menu a {
    text-decoration: none;
    color: var(--text-light);
    font-weight: 400;
    font-size: 0.95rem;
    transition: var(--transition);
    padding: 0.25rem 0;
    position: relative;
}

.nav-menu a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 1px;
    background-color: var(--primary-color);
    transition: var(--transition);
}

.nav-menu a:hover,
.nav-menu a.active {
    color: var(--text-color);
}

.nav-menu a:hover::after,
.nav-menu a.active::after {
    width: 100%;
}

/* Main Content */
main {
    min-height: calc(100vh - 200px);
}

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

/* Hero Section */
.hero {
    background-color: var(--bg-color);
    padding: 6rem var(--spacing) 4rem;
}

.hero-content {
    max-width: var(--max-width);
    margin: 0 auto;
    display: grid;
    grid-template-columns: 1fr 1.5fr;
    gap: 4rem;
    align-items: center;
}

.cover-container {
    display: flex;
    justify-content: center;
    align-items: center;
}

.cover-image {
    max-width: 100%;
    height: auto;
    max-height: 500px;
}

.hero-text h1 {
    font-size: 2.75rem;
    margin-bottom: 1.5rem;
    line-height: 1.1;
    font-weight: 500;
    letter-spacing: -0.03em;
    color: var(--text-color);
}

.subtitle {
    font-size: 1.15rem;
    margin-bottom: 1.5rem;
    color: var(--text-light);
    font-weight: 400;
    line-height: 1.6;
}

.author-name {
    font-size: 1rem;
    margin-bottom: 2.5rem;
    color: var(--text-light);
}

.author-name a {
    color: var(--text-color);
    text-decoration: none;
    border-bottom: 1px solid var(--border-color);
    transition: var(--transition);
}

.author-name a:hover {
    border-bottom-color: var(--text-color);
}

.cta-buttons {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.875rem 1.75rem;
    border-radius: var(--border-radius);
    text-decoration: none;
    font-weight: 400;
    font-size: 0.95rem;
    transition: var(--transition);
    border: 1px solid transparent;
    cursor: pointer;
    letter-spacing: -0.01em;
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.btn-primary:hover {
    background-color: var(--primary-hover);
    border-color: var(--primary-hover);
}

.btn-secondary {
    background-color: transparent;
    color: var(--text-color);
    border-color: var(--border-color);
}

.btn-secondary:hover {
    border-color: var(--text-color);
    color: var(--text-color);
}

.btn-outline {
    background-color: transparent;
    color: var(--text-color);
    border-color: var(--border-color);
}

.btn-outline:hover {
    border-color: var(--text-color);
    background-color: var(--text-color);
    color: white;
}

.btn-amazon {
    background-color: #ff9900;
    color: white;
    font-weight: 400;
    border-color: #ff9900;
}

.btn-amazon:hover {
    background-color: #e68900;
    border-color: #e68900;
}

/* Sections */
section {
    padding: 5rem var(--spacing);
}

section.overview {
    background-color: var(--bg-light);
}

section.features {
    background-color: var(--bg-color);
}

section.companion {
    background-color: var(--bg-light);
}

section.purchase {
    background-color: var(--bg-light);
    text-align: center;
    border-top: 1px solid var(--border-color);
    border-bottom: 1px solid var(--border-color);
}

section.purchase h2 {
    color: var(--text-color);
    margin-bottom: 1rem;
    font-weight: 500;
}

section.purchase .lead {
    color: var(--text-light);
    font-size: 1.05rem;
    margin-bottom: 2rem;
    font-weight: 400;
}

.page-header {
    background-color: var(--bg-color);
    padding: 4rem var(--spacing) 2rem;
    border-bottom: 1px solid var(--border-color);
}

.page-header h1 {
    max-width: var(--max-width);
    margin: 0 auto;
    font-size: 2.5rem;
    font-weight: 500;
    letter-spacing: -0.03em;
    color: var(--text-color);
}

.content {
    padding: 4rem var(--spacing);
}

/* Typography */
h2 {
    font-size: 1.75rem;
    margin-bottom: 1.5rem;
    margin-top: 3rem;
    color: var(--text-color);
    font-weight: 500;
    letter-spacing: -0.02em;
    line-height: 1.3;
}

h2:first-of-type {
    margin-top: 0;
}

h3 {
    font-size: 1.35rem;
    margin-bottom: 1rem;
    margin-top: 2.5rem;
    color: var(--text-color);
    font-weight: 500;
    letter-spacing: -0.01em;
}

.lead {
    font-size: 1.15rem;
    color: var(--text-light);
    margin-bottom: 2rem;
    font-weight: 400;
    line-height: 1.7;
}

p {
    margin-bottom: 1.5rem;
    line-height: 1.7;
}

ul, ol {
    margin-bottom: 1.5rem;
    padding-left: 1.5rem;
}

li {
    margin-bottom: 0.75rem;
    line-height: 1.7;
}

code {
    background-color: var(--bg-light);
    padding: 0.15rem 0.4rem;
    border-radius: 3px;
    font-family: 'Monaco', 'Menlo', 'Ubuntu Mono', 'Consolas', 'source-code-pro', monospace;
    font-size: 0.9em;
    color: var(--text-color);
    border: 1px solid var(--border-color);
}

li code {
    background-color: var(--bg-light);
    padding: 0.1rem 0.3rem;
}

/* Feature Grid */
.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2.5rem;
    margin-top: 3rem;
}

.feature-card {
    background-color: var(--bg-color);
    padding: 0;
    border: none;
    transition: var(--transition);
}

.feature-card:hover {
    transform: none;
}

.feature-card h3 {
    color: var(--text-color);
    margin-top: 0;
    margin-bottom: 1rem;
    font-size: 1.25rem;
}

.feature-card p {
    color: var(--text-light);
    margin-bottom: 0;
}

/* Book Content */
.book-content {
    max-width: 700px;
    margin: 0 auto;
}

.image-container {
    margin: 3rem 0;
    text-align: center;
}

.overview-image {
    max-width: 100%;
    height: auto;
}

/* Author Content */
.author-content {
    max-width: 700px;
    margin: 0 auto;
}

.author-intro {
    margin-bottom: 3rem;
}

.author-photo-container {
    text-align: center;
    margin-bottom: 2rem;
}

.author-photo {
    width: 200px;
    height: 200px;
    object-fit: cover;
    border-radius: 50%;
    border: 1px solid var(--border-color);
}

.author-bio,
.author-cv,
.author-contact {
    margin-bottom: 3rem;
}

.cv-link {
    margin-top: 1.5rem;
}

/* Companion Content */
.companion-content {
    max-width: 700px;
    margin: 0 auto;
}

.repository-info,
.repository-features,
.repository-access {
    margin-bottom: 3rem;
}

.repository-link-box {
    background-color: var(--bg-light);
    padding: 2.5rem;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    text-align: center;
    margin: 2.5rem 0;
}

.repository-link-box h3 {
    color: var(--text-color);
    margin-top: 0;
    font-size: 1.25rem;
}

.repository-link-box .note {
    margin-top: 1.5rem;
    font-size: 0.9rem;
    color: var(--text-light);
    font-style: normal;
}

.companion-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
    margin-top: 2rem;
}

/* Purchase Section */
.purchase-section {
    margin: 4rem 0;
    padding: 3rem 2.5rem;
    background-color: var(--bg-light);
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    text-align: center;
}

.purchase-section h3 {
    color: var(--text-color);
    margin-top: 0;
    margin-bottom: 1rem;
    font-size: 1.35rem;
}

.purchase-section p {
    margin-bottom: 1.5rem;
    color: var(--text-light);
}

/* CTA Section */
.cta-section {
    margin-top: 4rem;
    padding-top: 3rem;
    border-top: 1px solid var(--border-color);
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

/* Footer */
footer {
    background-color: var(--bg-color);
    border-top: 1px solid var(--border-color);
    padding: 3rem var(--spacing);
    text-align: center;
    color: var(--text-light);
    font-size: 0.9rem;
}

footer p {
    margin-bottom: 0.5rem;
}

/* Responsive Design */
@media (max-width: 768px) {
    :root {
        --spacing: 1.5rem;
    }

    .hero {
        padding: 4rem var(--spacing) 3rem;
    }

    .hero-content {
        grid-template-columns: 1fr;
        gap: 3rem;
        text-align: left;
    }

    .hero-text h1 {
        font-size: 2rem;
    }

    .subtitle {
        font-size: 1.05rem;
    }

    .nav-container {
        flex-direction: column;
        align-items: flex-start;
        padding: 1.25rem var(--spacing);
    }

    .nav-menu {
        margin-top: 1rem;
        gap: 1.5rem;
    }

    .feature-grid {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .page-header {
        padding: 3rem var(--spacing) 1.5rem;
    }

    .page-header h1 {
        font-size: 2rem;
    }

    .content {
        padding: 3rem var(--spacing);
    }

    section {
        padding: 4rem var(--spacing);
    }

    h2 {
        font-size: 1.5rem;
        margin-top: 2.5rem;
    }

    h3 {
        font-size: 1.2rem;
        margin-top: 2rem;
    }
}

@media (max-width: 480px) {
    :root {
        --spacing: 1.25rem;
    }

    section {
        padding: 3rem var(--spacing);
    }

    .hero {
        padding: 3rem var(--spacing) 2rem;
    }

    .hero-text h1 {
        font-size: 1.75rem;
    }

    .cta-buttons {
        flex-direction: column;
    }

    .btn {
        width: 100%;
        text-align: center;
    }

    .purchase-section {
        padding: 2rem 1.5rem;
    }
}