/* =============================================
   Base & Reset
   ============================================= */
*, *::before, *::after {
    box-sizing: border-box;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

:root {
    --bg: #e8eaf2;
    --surface: #eef0f5;
    --white: #ffffff;
    --shadow-out: 8px 8px 20px #c8cad4, -8px -8px 20px #ffffff;
    --shadow-in: inset 4px 4px 10px #c8cad4, inset -4px -4px 10px #ffffff;
    --shadow-hover: 12px 12px 28px #bec0ca, -12px -12px 28px #ffffff;
    --blue: #4a8ff5;
    --blue-dark: #2d72d9;
    --text-primary: #1a1d2e;
    --text-secondary: #6b7280;
    --text-muted: #9ca3af;
    --border: rgba(255,255,255,0.7);
    --radius: 20px;
    --radius-sm: 12px;
    --radius-pill: 50px;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background-color: var(--bg);
    color: var(--text-primary);
    font-weight: 400;
    letter-spacing: -0.01em;
    line-height: 1.6;
}

h1, h2, h3, h4 {
    font-family: 'Inter', sans-serif;
    font-weight: 700;
    letter-spacing: -0.03em;
    color: var(--text-primary);
    line-height: 1.1;
}

/* =============================================
   Navigation
   ============================================= */
.navbar {
    position: sticky;
    top: 0;
    z-index: 50;
    background-color: var(--bg);
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.06);
    border-bottom: 1px solid var(--border);
}

.navbar-inner {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 2rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 70px;
}

.navbar-brand {
    font-size: 1.4rem;
    font-weight: 800;
    color: var(--text-primary);
    text-decoration: none;
    letter-spacing: -0.04em;
}

.navbar-brand span {
    color: var(--blue);
}

.navbar-links {
    display: flex;
    align-items: center;
    gap: 0.25rem;
    list-style: none;
    margin: 0;
    padding: 0;
}

.nav-link {
    text-decoration: none;
    color: var(--text-secondary);
    font-size: 0.9rem;
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    transition: all 0.2s ease;
    position: relative;
}

.nav-link:hover {
    color: var(--text-primary);
    background: rgba(74, 143, 245, 0.08);
}

.nav-link.active {
    color: var(--blue);
    font-weight: 600;
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 1rem;
    right: 1rem;
    height: 2px;
    background: var(--blue);
    border-radius: 2px;
}

.btn-cta {
    background: var(--blue);
    color: white;
    font-weight: 700;
    font-size: 0.85rem;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    padding: 0.65rem 1.5rem;
    border-radius: var(--radius-pill);
    border: none;
    cursor: pointer;
    text-decoration: none;
    display: inline-block;
    transition: all 0.25s ease;
    box-shadow: 0 6px 20px rgba(74, 143, 245, 0.4);
}

.btn-cta:hover {
    background: var(--blue-dark);
    transform: translateY(-2px);
    box-shadow: 0 10px 28px rgba(74, 143, 245, 0.5);
}

.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-secondary);
    padding: 0.5rem;
}

.mobile-menu {
    display: none;
    padding: 0.5rem 1.5rem 1rem;
    background: var(--bg);
    border-top: 1px solid var(--border);
}

.mobile-menu .nav-link {
    display: block;
    padding: 0.75rem 1rem;
    margin-bottom: 0.25rem;
}

/* =============================================
   Hero Section
   ============================================= */
.hero {
    background: var(--bg);
    padding: 5rem 2rem;
    text-align: center;
    position: relative;
    overflow: hidden;
    min-height: 65vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.hero::before {
    content: '';
    position: absolute;
    width: 500px;
    height: 500px;
    border-radius: 50%;
    background: radial-gradient(circle, rgba(74, 143, 245, 0.08) 0%, transparent 70%);
    top: -100px;
    right: -100px;
    pointer-events: none;
}

.hero::after {
    content: '';
    position: absolute;
    width: 400px;
    height: 400px;
    border-radius: 50%;
    background: radial-gradient(circle, rgba(74, 143, 245, 0.06) 0%, transparent 70%);
    bottom: -80px;
    left: -80px;
    pointer-events: none;
}

.hero-avatar {
    width: 160px;
    height: 160px;
    border-radius: 50%;
    object-fit: cover;
    box-shadow: var(--shadow-out);
    border: 5px solid var(--white);
    margin-bottom: 2rem;
    position: relative;
    z-index: 1;
}

.hero-title {
    font-size: clamp(2.5rem, 6vw, 5rem);
    font-weight: 900;
    letter-spacing: -0.04em;
    color: var(--text-primary);
    margin-bottom: 1.25rem;
    position: relative;
    z-index: 1;
}

.hero-subtitle {
    font-size: 1.15rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
    font-weight: 400;
    line-height: 1.7;
    position: relative;
    z-index: 1;
}

/* =============================================
   Layout
   ============================================= */
.main-content {
    max-width: 1280px;
    margin: 0 auto;
    padding: 4rem 2rem 6rem;
}

/* =============================================
   Section Headers
   ============================================= */
.section-header {
    text-align: center;
    margin-bottom: 4rem;
}

.section-title {
    font-size: clamp(1.8rem, 4vw, 3rem);
    font-weight: 800;
    margin-bottom: 0.75rem;
}

.section-subtitle {
    font-size: 1rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
    line-height: 1.7;
}

/* =============================================
   Cards (Neumorphic)
   ============================================= */
.neu-card {
    background: var(--surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow-out);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    border: 1px solid var(--border);
}

.neu-card:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-6px);
}

.neu-card-inset {
    background: var(--bg);
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow-in);
    border: 1px solid rgba(255,255,255,0.5);
}

/* =============================================
   Timeline
   ============================================= */
.timeline-section {
    margin-bottom: 6rem;
}

.timeline-wrapper {
    position: relative;
    max-width: 900px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.timeline-line {
    position: absolute;
    height: 100%;
    width: 2px;
    background: linear-gradient(to bottom, transparent, var(--blue), transparent);
    left: 50%;
    transform: translateX(-50%);
    opacity: 0.3;
}

.timeline-item-container {
    width: 100%;
    display: flex;
}

.timeline-item-container:nth-child(odd) {
    justify-content: flex-start;
    padding-right: calc(50% + 2rem);
}

.timeline-item-container:nth-child(even) {
    justify-content: flex-end;
    padding-left: calc(50% + 2rem);
}

.timeline-item-container + .timeline-item-container {
    margin-top: 2rem;
}

.timeline-card {
    background: var(--surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow-out);
    padding: 2rem;
    position: relative;
    transition: all 0.3s ease;
    border: 1px solid var(--border);
    width: 100%;
}

.timeline-card:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-4px);
}

.timeline-dot {
    position: absolute;
    width: 16px;
    height: 16px;
    border-radius: 50%;
    background: var(--blue);
    box-shadow: 0 0 0 4px var(--bg), 0 0 0 6px rgba(74, 143, 245, 0.3);
    top: 50%;
    transform: translateY(-50%);
}

.timeline-item-container:nth-child(odd) .timeline-dot {
    right: -2.6rem;
}

.timeline-item-container:nth-child(even) .timeline-dot {
    left: -2.6rem;
}

.timeline-label {
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--blue);
    margin-bottom: 0.5rem;
}

.timeline-card h3 {
    font-size: 1.2rem;
    font-weight: 700;
    margin-bottom: 0.75rem;
}

.timeline-card p {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.65;
}

/* =============================================
   Tab Methods Section
   ============================================= */
.methods-section {
    margin-bottom: 6rem;
}

.tab-group {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
    justify-content: center;
}

.tab-button {
    padding: 0.75rem 1.75rem;
    font-size: 0.9rem;
    font-weight: 600;
    border-radius: var(--radius-pill);
    border: none;
    cursor: pointer;
    transition: all 0.25s ease;
    background: var(--surface);
    color: var(--text-secondary);
    box-shadow: var(--shadow-out);
}

.tab-button:hover {
    color: var(--text-primary);
    transform: translateY(-2px);
}

.tab-button.active {
    background: var(--blue);
    color: white;
    box-shadow: 0 6px 20px rgba(74, 143, 245, 0.4);
    transform: translateY(-2px);
}

.tab-content {
    padding: 2.5rem;
    min-height: 200px;
}

.tab-content h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.tab-content p {
    color: var(--text-secondary);
    font-size: 1rem;
    line-height: 1.75;
}

/* =============================================
   Blueprint / Stats
   ============================================= */
.blueprint-section {
    margin-bottom: 6rem;
}

.stat-card {
    padding: 2.5rem 2rem;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.stat-number {
    font-size: clamp(2rem, 5vw, 3.5rem);
    font-weight: 900;
    color: var(--text-primary);
    margin-bottom: 0.75rem;
    letter-spacing: -0.04em;
    line-height: 1;
}

.stat-number span {
    display: block;
    width: 40px;
    height: 4px;
    background: var(--blue);
    border-radius: 2px;
    margin: 1rem auto 0;
}

.stat-label {
    font-weight: 700;
    font-size: 1rem;
    color: var(--text-primary);
    margin-bottom: 0.75rem;
}

.stat-desc {
    font-size: 0.875rem;
    color: var(--text-secondary);
    line-height: 1.65;
}

/* =============================================
   YouTube Section
   ============================================= */
.youtube-section {
    margin-bottom: 6rem;
    padding: 3.5rem;
    text-align: center;
}

.youtube-section h2 {
    font-size: clamp(1.8rem, 4vw, 2.75rem);
    margin-bottom: 1rem;
}

.youtube-section p {
    color: var(--text-secondary);
    max-width: 550px;
    margin: 0 auto 2.5rem;
    line-height: 1.7;
}

.btn-primary {
    display: inline-block;
    background: var(--blue);
    color: white;
    font-weight: 700;
    font-size: 0.95rem;
    padding: 1rem 2.5rem;
    border-radius: var(--radius-pill);
    text-decoration: none;
    transition: all 0.25s ease;
    box-shadow: 0 8px 24px rgba(74, 143, 245, 0.4);
}

.btn-primary:hover {
    background: var(--blue-dark);
    transform: translateY(-3px);
    box-shadow: 0 12px 30px rgba(74, 143, 245, 0.5);
}

/* =============================================
   Books Section
   ============================================= */
.books-section {
    margin-bottom: 4rem;
}

.filter-group {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 0.75rem;
    margin-bottom: 3rem;
}

.filter-btn {
    padding: 0.65rem 1.4rem;
    font-size: 0.875rem;
    font-weight: 600;
    border-radius: var(--radius-pill);
    border: none;
    cursor: pointer;
    transition: all 0.25s ease;
    background: var(--surface);
    color: var(--text-secondary);
    box-shadow: var(--shadow-out);
}

.filter-btn:hover {
    color: var(--text-primary);
    transform: translateY(-2px);
}

.filter-btn.active {
    background: var(--blue);
    color: white;
    box-shadow: 0 6px 20px rgba(74, 143, 245, 0.4);
    transform: translateY(-2px);
}

.book-card {
    background: var(--surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow-out);
    overflow: hidden;
    display: flex;
    flex-direction: column;
    transition: all 0.3s ease;
    border: 1px solid var(--border);
}

.book-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-hover);
}

.book-cover {
    width: 100%;
    height: 280px;
    object-fit: contain;
    padding: 1.5rem;
    background: rgba(255,255,255,0.6);
}

.book-body {
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    flex-grow: 1;
}

.book-title {
    font-weight: 700;
    font-size: 0.95rem;
    color: var(--text-primary);
    line-height: 1.4;
    flex-grow: 1;
    margin-bottom: 1.25rem;
}

.btn-amazon {
    display: block;
    text-align: center;
    background: var(--blue);
    color: white;
    font-weight: 600;
    font-size: 0.85rem;
    padding: 0.75rem 1rem;
    border-radius: var(--radius-sm);
    text-decoration: none;
    transition: all 0.25s ease;
    box-shadow: 0 4px 14px rgba(74, 143, 245, 0.3);
}

.btn-amazon:hover {
    background: var(--blue-dark);
    transform: translateY(-2px);
    box-shadow: 0 6px 18px rgba(74, 143, 245, 0.45);
}

/* =============================================
   Footer
   ============================================= */
.footer {
    background: var(--text-primary);
    color: white;
    padding: 5rem 2rem;
    text-align: center;
}

.footer h3 {
    color: white;
    font-size: 2rem;
    margin-bottom: 0.75rem;
}

.footer p {
    color: rgba(255,255,255,0.6);
    max-width: 450px;
    margin: 0 auto 2rem;
    line-height: 1.7;
}

.btn-donate {
    display: inline-block;
    background: white;
    color: var(--text-primary);
    font-weight: 700;
    font-size: 0.95rem;
    padding: 1rem 2.5rem;
    border-radius: var(--radius-pill);
    text-decoration: none;
    transition: all 0.25s ease;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.3);
}

.btn-donate:hover {
    background: #f0f0f0;
    transform: translateY(-3px);
    box-shadow: 0 12px 30px rgba(0, 0, 0, 0.4);
}

.footer-copyright {
    margin-top: 3rem;
    font-size: 0.75rem;
    color: rgba(255,255,255,0.3);
    letter-spacing: 0.1em;
}

/* =============================================
   Responsive
   ============================================= */
@media (max-width: 768px) {
    .navbar-links,
    .navbar-links + a {
        display: none;
    }

    .mobile-menu-btn {
        display: flex;
        align-items: center;
    }

    .mobile-menu.open {
        display: block;
    }

    .timeline-item-container:nth-child(odd),
    .timeline-item-container:nth-child(even) {
        padding-right: 0;
        padding-left: 0;
        justify-content: center;
    }

    .timeline-line { display: none; }
    .timeline-dot { display: none; }

    .main-content {
        padding: 2.5rem 1.25rem 4rem;
    }

    .youtube-section {
        padding: 2.5rem 1.5rem;
    }
}

@media (max-width: 640px) {
    .tab-group {
        flex-direction: column;
    }

    .tab-button {
        text-align: center;
    }
}