/* ===================================
   Yuanqi Tech Toolkit - Global Styles
   =================================== */

/* --- CSS Reset & Base --- */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary-color: #64748b;
    --accent-color: #0ea5e9;
    --bg-color: #ffffff;
    --bg-light: #f8fafc;
    --bg-dark: #0f172a;
    --text-color: #1e293b;
    --text-light: #64748b;
    --text-white: #f8fafc;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
    --radius: 8px;
    --max-width: 1200px;
    --transition: all 0.3s ease;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    color: var(--text-color);
    background-color: var(--bg-color);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

a {
    text-decoration: none;
    color: inherit;
    transition: var(--transition);
}

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

.container {
    width: 100%;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 20px;
}

/* --- Header --- */
.site-header {
    background: var(--bg-color);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    backdrop-filter: blur(10px);
    background: rgba(255, 255, 255, 0.95);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 20px;
    max-width: var(--max-width);
    margin: 0 auto;
}

.brand {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 700;
    font-size: 1.1rem;
    color: var(--primary-color);
}

.brand-icon {
    font-size: 1.4rem;
}

.main-nav {
    display: flex;
    gap: 28px;
    align-items: center;
}

.main-nav > a,
.main-nav .nav-dropdown > a {
    font-size: 0.95rem;
    color: var(--text-light);
    font-weight: 500;
    position: relative;
    padding: 4px 0;
}

.main-nav a:hover,
.main-nav a.active {
    color: var(--primary-color);
}

.main-nav a.active::after {
    content: '';
    position: absolute;
    bottom: -6px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--primary-color);
    border-radius: 1px;
}

/* --- Dropdown Menu --- */
.nav-dropdown {
    position: relative;
}

.nav-dropdown > a::after {
    content: '';
    margin-left: 4px;
    font-size: 0.7em;
    display: inline-block;
    vertical-align: middle;
}

.dropdown-menu {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    min-width: 220px;
    padding: 8px 0;
    z-index: 100;
}

.dropdown-menu a {
    display: block;
    padding: 10px 20px;
    font-size: 0.9rem;
    color: var(--text-light);
    white-space: nowrap;
}

.dropdown-menu a:hover {
    background: var(--bg-light);
    color: var(--primary-color);
}

.nav-dropdown:hover .dropdown-menu {
    display: block;
}

.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-color);
    padding: 4px;
}

/* --- Hero Section --- */
.hero {
    background: linear-gradient(135deg, var(--bg-dark) 0%, #1e3a5f 100%);
    color: var(--text-white);
    padding: 100px 0 80px;
    text-align: center;
}

.hero h1 {
    font-size: 2.8rem;
    font-weight: 800;
    margin-bottom: 16px;
    letter-spacing: -0.5px;
}

.hero p {
    font-size: 1.15rem;
    color: #cbd5e1;
    max-width: 600px;
    margin: 0 auto 32px;
}

/* --- Buttons --- */
.btn {
    display: inline-block;
    padding: 12px 28px;
    border-radius: var(--radius);
    font-weight: 600;
    font-size: 0.95rem;
    cursor: pointer;
    transition: var(--transition);
    border: none;
    text-align: center;
}

.btn-primary {
    background: var(--primary-color);
    color: #fff;
}

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

.btn-secondary:hover {
    background: var(--primary-color);
    color: #fff;
}

/* --- Tools Section --- */
.tools-section {
    padding: 80px 0;
    background: var(--bg-light);
}

.section-title {
    text-align: center;
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 48px;
    color: var(--text-color);
}

.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
    gap: 28px;
}

.tool-card {
    background: var(--bg-color);
    border-radius: var(--radius);
    padding: 32px;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
    transition: var(--transition);
    display: flex;
    flex-direction: column;
}

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

.tool-icon {
    font-size: 2.5rem;
    margin-bottom: 16px;
}

.tool-card h3 {
    font-size: 1.25rem;
    margin-bottom: 12px;
    color: var(--text-color);
}

.tool-desc {
    color: var(--text-light);
    font-size: 0.95rem;
    margin-bottom: 16px;
    flex-grow: 1;
}

.tool-features {
    list-style: none;
    margin-bottom: 24px;
}

.tool-features li {
    padding: 4px 0;
    color: var(--text-light);
    font-size: 0.9rem;
}

.tool-features li::before {
    content: '\2713';
    color: var(--primary-color);
    margin-right: 8px;
    font-weight: 700;
}

.tool-actions {
    display: flex;
    gap: 12px;
    margin-top: auto;
}

.tool-actions .btn {
    flex: 1;
    padding: 10px 16px;
    font-size: 0.88rem;
}

/* --- Why Section --- */
.why-section {
    padding: 80px 0;
}

.why-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 32px;
}

.why-item {
    text-align: center;
    padding: 24px;
}

.why-icon {
    font-size: 2.5rem;
    margin-bottom: 16px;
}

.why-item h3 {
    font-size: 1.15rem;
    margin-bottom: 8px;
}

.why-item p {
    color: var(--text-light);
    font-size: 0.95rem;
}

/* --- CTA Section --- */
.cta-section {
    padding: 80px 0;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--accent-color) 100%);
    color: #fff;
    text-align: center;
}

.cta-section h2 {
    font-size: 2rem;
    margin-bottom: 12px;
}

.cta-section p {
    font-size: 1.1rem;
    opacity: 0.9;
    margin-bottom: 28px;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.cta-section .btn {
    background: #fff;
    color: var(--primary-color);
}

.cta-section .btn:hover {
    background: var(--bg-light);
    transform: translateY(-1px);
    box-shadow: var(--shadow-lg);
}

/* --- Footer --- */
.site-footer {
    background: var(--bg-dark);
    color: var(--text-light);
    padding: 40px 0 24px;
    margin-top: auto;
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: 32px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.footer-links a {
    color: var(--text-light);
    font-size: 0.9rem;
}

.footer-links a:hover {
    color: var(--text-white);
}

.copyright {
    text-align: center;
    font-size: 0.85rem;
    opacity: 0.7;
}

/* --- Page Content Layout --- */
.page-content {
    padding: 60px 0;
    flex: 1;
}

.page-content h1 {
    font-size: 2rem;
    margin-bottom: 24px;
}

.page-content h2 {
    font-size: 1.5rem;
    margin-top: 32px;
    margin-bottom: 16px;
}

.page-content h3 {
    font-size: 1.2rem;
    margin-top: 24px;
    margin-bottom: 12px;
}

.page-content p {
    margin-bottom: 16px;
    color: var(--text-light);
}

.page-content ul,
.page-content ol {
    margin-bottom: 16px;
    padding-left: 24px;
    color: var(--text-light);
}

.page-content li {
    margin-bottom: 8px;
}

/* --- Tool Detail Page --- */
.tool-hero {
    background: linear-gradient(135deg, var(--bg-dark) 0%, #1e3a5f 100%);
    color: var(--text-white);
    padding: 60px 0 40px;
}

.tool-hero h1 {
    font-size: 2.2rem;
    margin-bottom: 12px;
}

.tool-hero p {
    color: #cbd5e1;
    font-size: 1.1rem;
    max-width: 700px;
}

.tool-info-grid {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 40px;
    margin-top: 40px;
}

.tool-sidebar {
    background: var(--bg-light);
    border-radius: var(--radius);
    padding: 24px;
    border: 1px solid var(--border-color);
    position: sticky;
    top: 100px;
    height: fit-content;
}

.tool-sidebar h3 {
    margin-bottom: 16px;
    font-size: 1.1rem;
}

.download-info {
    margin-bottom: 24px;
}

.download-info p {
    font-size: 0.9rem;
    margin-bottom: 12px;
}

.step-list {
    list-style: none;
    counter-reset: step-counter;
}

.step-list li {
    counter-increment: step-counter;
    padding: 12px 0 12px 40px;
    position: relative;
    border-bottom: 1px solid var(--border-color);
    font-size: 0.95rem;
}

.step-list li:last-child {
    border-bottom: none;
}

.step-list li::before {
    content: counter(step-counter);
    position: absolute;
    left: 0;
    top: 12px;
    width: 24px;
    height: 24px;
    background: var(--primary-color);
    color: #fff;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.8rem;
    font-weight: 700;
}

/* --- Modal --- */
.modal-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.6);
    z-index: 9999;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.modal-overlay.active {
    display: flex;
}

.modal {
    background: var(--bg-color);
    border-radius: var(--radius);
    max-width: 560px;
    width: 100%;
    max-height: 85vh;
    overflow-y: auto;
    box-shadow: var(--shadow-lg);
}

.modal-header {
    padding: 24px 28px 0;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-header h3 {
    font-size: 1.3rem;
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-light);
    padding: 4px;
    line-height: 1;
}

.modal-close:hover {
    color: var(--text-color);
}

.modal-body {
    padding: 20px 28px 28px;
}

.modal-body p {
    font-size: 0.95rem;
    color: var(--text-light);
    margin-bottom: 16px;
}

.terms-box {
    background: var(--bg-light);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 20px;
    margin: 20px 0;
    max-height: 200px;
    overflow-y: auto;
    font-size: 0.9rem;
    line-height: 1.7;
}

.terms-box h4 {
    margin-bottom: 12px;
    font-size: 1rem;
}

.terms-box ul {
    padding-left: 20px;
}

.terms-box li {
    margin-bottom: 8px;
}

.checkbox-group {
    display: flex;
    align-items: flex-start;
    gap: 10px;
    margin: 20px 0;
}

.checkbox-group input[type="checkbox"] {
    margin-top: 3px;
    accent-color: var(--primary-color);
}

.checkbox-group label {
    font-size: 0.9rem;
    color: var(--text-color);
    cursor: pointer;
}

.modal-actions {
    display: flex;
    gap: 12px;
    margin-top: 20px;
}

.modal-actions .btn {
    flex: 1;
    padding: 12px;
}

.btn-disabled {
    opacity: 0.5;
    cursor: not-allowed;
    pointer-events: none;
}

/* --- Customize Page --- */
.service-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 24px;
    margin: 32px 0;
}

.service-card {
    background: var(--bg-light);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 28px;
}

.service-card h3 {
    margin-bottom: 12px;
}

.service-card p {
    font-size: 0.95rem;
}

.contact-form {
    max-width: 500px;
    margin: 32px auto 0;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 6px;
    font-weight: 600;
    font-size: 0.95rem;
}

.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 12px 16px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-size: 0.95rem;
    font-family: inherit;
    transition: var(--transition);
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-group textarea {
    resize: vertical;
    min-height: 120px;
}

/* --- Responsive --- */
@media (max-width: 768px) {
    .main-nav {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--bg-color);
        flex-direction: column;
        padding: 20px;
        gap: 16px;
        border-bottom: 1px solid var(--border-color);
        box-shadow: var(--shadow-md);
    }

    .main-nav.open {
        display: flex;
    }

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

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

    .hero p {
        font-size: 1rem;
    }

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

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

    .tool-sidebar {
        position: static;
    }

    .footer-links {
        flex-direction: column;
        align-items: center;
        gap: 16px;
    }

    .modal-actions {
        flex-direction: column;
    }

    .tool-actions {
        flex-direction: column;
    }
}

@media (max-width: 480px) {
    .hero {
        padding: 60px 0 50px;
    }

    .hero h1 {
        font-size: 1.6rem;
    }

    .section-title {
        font-size: 1.5rem;
    }

    .tool-card {
        padding: 24px;
    }

    .page-content {
        padding: 40px 0;
    }
}

/* --- Positioning Section --- */
.positioning-section {
    padding: 80px 0;
    background: var(--bg-light);
}

.positioning-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 32px;
}

.positioning-item {
    text-align: center;
    padding: 32px 24px;
    background: var(--bg-color);
    border-radius: var(--radius);
    border: 1px solid var(--border-color);
}

.positioning-icon {
    font-size: 2.5rem;
    margin-bottom: 16px;
}

.positioning-item h3 {
    font-size: 1.15rem;
    margin-bottom: 12px;
}

.positioning-item p {
    color: var(--text-light);
    font-size: 0.95rem;
}

/* --- How It Works --- */
.how-it-works {
    padding: 80px 0;
}

.steps-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 40px;
}

.step-item {
    text-align: center;
    padding: 20px;
}

.step-number {
    width: 48px;
    height: 48px;
    background: var(--primary-color);
    color: #fff;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.3rem;
    font-weight: 700;
    margin: 0 auto 20px;
}

.step-item h3 {
    font-size: 1.15rem;
    margin-bottom: 10px;
}

.step-item p {
    color: var(--text-light);
    font-size: 0.95rem;
}

/* --- Categories Preview --- */
.categories-preview {
    padding: 80px 0;
    background: var(--bg-light);
}

.categories-grid {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 24px;
}

.category-card {
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 28px 24px;
    text-align: center;
    transition: var(--transition);
    display: block;
}

.category-card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-4px);
    border-color: var(--primary-color);
}

.cat-icon {
    font-size: 2.2rem;
    margin-bottom: 14px;
}

.category-card h3 {
    font-size: 1.05rem;
    margin-bottom: 10px;
    color: var(--text-color);
}

.category-card p {
    color: var(--text-light);
    font-size: 0.9rem;
}

/* --- Tool Category (tools.html) --- */
.tool-category {
    margin-bottom: 60px;
}

.tool-category:last-child {
    margin-bottom: 0;
}

.category-title {
    font-size: 1.5rem;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--border-color);
    margin-bottom: 28px;
    color: var(--text-color);
}

.tool-card.coming-soon {
    opacity: 0.7;
}

.tool-card.coming-soon:hover {
    transform: none;
    box-shadow: var(--shadow-sm);
}

/* --- Responsive --- */
@media (max-width: 768px) {
    .main-nav {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--bg-color);
        flex-direction: column;
        padding: 20px;
        gap: 16px;
        border-bottom: 1px solid var(--border-color);
        box-shadow: var(--shadow-md);
    }

    .main-nav.open {
        display: flex;
    }

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

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

    .hero p {
        font-size: 1rem;
    }

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

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

    .tool-sidebar {
        position: static;
    }

    .footer-links {
        flex-direction: column;
        align-items: center;
        gap: 16px;
    }

    .modal-actions {
        flex-direction: column;
    }

    .tool-actions {
        flex-direction: column;
    }

    /* Mobile dropdown */
    .dropdown-menu {
        position: static;
        box-shadow: none;
        border: none;
        background: var(--bg-light);
        margin-top: 8px;
    }

    .nav-dropdown.open .dropdown-menu {
        display: block;
    }
}

@media (max-width: 480px) {
    .hero {
        padding: 60px 0 50px;
    }

    .hero h1 {
        font-size: 1.6rem;
    }

    .section-title {
        font-size: 1.5rem;
    }

    .tool-card {
        padding: 24px;
    }

    .page-content {
        padding: 40px 0;
    }

    .positioning-grid,
    .steps-row,
    .categories-grid {
        grid-template-columns: 1fr;
    }
}