/* ================================================
   Beijing Kesier Technology Development Co., Ltd.
   Responsive Stylesheet
   ================================================ */

/* Extra Large Screens */
@media (min-width: 1400px) {
    .container {
        max-width: 1320px;
    }
    
    .hero-title {
        font-size: 5rem;
    }
    
    .section {
        padding: 120px 0;
    }
}

/* Large Tablets */
@media (max-width: 1200px) {
    .container {
        max-width: 960px;
    }
    
    .hero-title {
        font-size: 3.5rem;
    }
    
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 20px;
    }
    
    .footer-grid {
        grid-template-columns: 1fr 1fr;
        gap: 40px;
    }
}

/* Tablets */
@media (max-width: 992px) {
    html {
        font-size: 15px;
    }
    
    .nav-links {
        gap: 30px;
    }
    
    .hero {
        padding: 120px 20px 80px;
    }
    
    .section {
        padding: 80px 0;
    }
    
    .about-grid,
    .services-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .app-grid {
        grid-template-columns: 1fr;
        gap: 40px;
    }
    
    .app-image {
        order: -1;
        margin-bottom: 30px;
    }
    
    .phone-mockup {
        width: 280px;
        height: 560px;
    }
}

/* Small Tablets */
@media (max-width: 768px) {
    html {
        font-size: 14px;
    }
    
    /* Mobile Navigation */
    .navbar {
        padding: 15px 0;
    }
    
    .navbar.scrolled {
        padding: 10px 0;
    }
    
    .menu-toggle {
        display: flex;
    }
    
    .nav-links {
        position: fixed;
        top: 0;
        right: -100%;
        width: 80%;
        max-width: 320px;
        height: 100vh;
        background: var(--secondary-color);
        flex-direction: column;
        justify-content: center;
        gap: 25px;
        padding: 40px 30px;
        transition: right 0.4s ease;
        box-shadow: -10px 0 30px rgba(0, 0, 0, 0.3);
        z-index: 1000;
    }
    
    .nav-links.active {
        right: 0;
    }
    
    .nav-links a {
        font-size: 1.3rem;
        padding: 10px 0;
        display: block;
    }
    
    .nav-overlay {
        position: fixed;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: rgba(0, 0, 0, 0.5);
        opacity: 0;
        visibility: hidden;
        transition: all 0.3s ease;
        z-index: 999;
    }
    
    .nav-overlay.active {
        opacity: 1;
        visibility: visible;
    }
    
    /* Hero Section */
    .hero {
        min-height: auto;
        padding: 140px 20px 80px;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-description {
        font-size: 1rem;
    }
    
    .hero-buttons {
        flex-direction: column;
        align-items: center;
        gap: 15px;
    }
    
    .btn {
        width: 100%;
        max-width: 260px;
        padding: 14px 28px;
        font-size: 0.9rem;
    }
    
    .scroll-indicator {
        display: none;
    }
    
    /* Sections */
    .section {
        padding: 60px 0;
    }
    
    .section-header {
        margin-bottom: 40px;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    /* About Section */
    .about-grid {
        grid-template-columns: 1fr;
        gap: 20px;
    }
    
    .about-card {
        padding: 30px 25px;
    }
    
    /* Services */
    .services-grid {
        grid-template-columns: 1fr;
        gap: 25px;
    }
    
    .service-card {
        margin: 0 auto;
        max-width: 400px;
    }
    
    /* App Showcase */
    .app-showcase {
        padding: 60px 0;
    }
    
    .app-content h2 {
        font-size: 1.8rem;
    }
    
    .app-features {
        gap: 15px;
    }
    
    .app-feature {
        gap: 12px;
    }
    
    .app-feature-icon {
        width: 36px;
        height: 36px;
        min-width: 36px;
    }
    
    .phone-mockup {
        width: 240px;
        height: 480px;
    }
    
    /* Stats */
    .stats-section {
        padding: 60px 0;
    }
    
    .stats-grid {
        grid-template-columns: 1fr 1fr;
        gap: 15px;
    }
    
    .stat-item {
        padding: 20px;
    }
    
    .stat-number {
        font-size: 2.5rem;
    }
    
    .stat-label {
        font-size: 0.85rem;
    }
    
    /* CTA */
    .cta-section {
        padding: 60px 20px;
    }
    
    .cta-content h2 {
        font-size: 1.8rem;
    }
    
    .cta-content p {
        font-size: 1rem;
    }
    
    /* Footer */
    .footer {
        padding: 60px 0 20px;
    }
    
    .footer-grid {
        grid-template-columns: 1fr;
        gap: 30px;
        text-align: center;
    }
    
    .footer-brand {
        max-width: 100%;
    }
    
    .footer-brand .logo {
        justify-content: center;
    }
    
    .social-links {
        justify-content: center;
    }
    
    .footer-column h4 {
        margin-bottom: 15px;
    }
    
    .footer-links {
        gap: 10px;
    }
    
    .footer-contact {
        align-items: center;
    }
    
    .footer-bottom {
        flex-direction: column;
        text-align: center;
        gap: 15px;
        padding-top: 20px;
    }
    
    .footer-legal {
        flex-direction: column;
        gap: 10px;
    }
    
    /* Page Header */
    .page-header {
        padding: 150px 20px 60px;
    }
    
    .page-header h1 {
        font-size: 2.2rem;
    }
    
    /* Forms */
    .form-group {
        margin-bottom: 20px;
    }
    
    .form-input,
    .form-textarea,
    .form-select {
        padding: 12px 15px;
        font-size: 0.95rem;
    }
    
    /* Grid Adjustments */
    .two-column-grid,
    .three-column-grid,
    .four-column-grid {
        grid-template-columns: 1fr;
    }
    
    /* Gallery */
    .gallery-grid {
        grid-template-columns: 1fr;
        gap: 15px;
    }
    
    /* Timeline */
    .timeline::before {
        left: 20px;
    }
    
    .timeline-item {
        padding-left: 50px;
    }
    
    /* Team */
    .team-grid {
        grid-template-columns: 1fr;
        gap: 25px;
    }
    
    /* Testimonials */
    .testimonial-slider {
        padding: 0 10px;
    }
    
    .testimonial-card {
        padding: 30px 25px;
    }
}

/* Mobile Devices */
@media (max-width: 576px) {
    html {
        font-size: 13px;
    }
    
    .container {
        padding: 0 15px;
    }
    
    /* Hero */
    .hero {
        padding: 130px 15px 60px;
    }
    
    .hero-subtitle {
        font-size: 0.9rem;
        letter-spacing: 2px;
    }
    
    .hero-title {
        font-size: 2rem;
        margin-bottom: 20px;
    }
    
    .hero-description {
        font-size: 0.95rem;
        margin-bottom: 30px;
    }
    
    /* Sections */
    .section {
        padding: 50px 0;
    }
    
    .section-header {
        margin-bottom: 30px;
    }
    
    .section-number {
        font-size: 0.8rem;
        letter-spacing: 2px;
    }
    
    .section-title {
        font-size: 1.75rem;
    }
    
    .section-subtitle {
        font-size: 0.95rem;
    }
    
    /* Cards */
    .about-card,
    .service-card .service-content {
        padding: 25px 20px;
    }
    
    .service-image {
        height: 180px;
    }
    
    /* Phone Mockup */
    .phone-mockup {
        width: 200px;
        height: 400px;
        border-radius: 30px;
    }
    
    .phone-screen {
        border-radius: 24px;
    }
    
    .phone-notch {
        width: 80px;
        height: 24px;
    }
    
    .phone-content svg {
        width: 60px;
        height: 60px;
    }
    
    /* Stats */
    .stats-grid {
        grid-template-columns: 1fr;
        gap: 10px;
    }
    
    .stat-item {
        padding: 15px;
        border-bottom: 1px solid var(--border-color);
    }
    
    .stat-item:last-child {
        border-bottom: none;
    }
    
    .stat-number {
        font-size: 2rem;
    }
    
    /* CTA */
    .cta-section {
        padding: 50px 15px;
    }
    
    .cta-btn {
        padding: 14px 30px;
        font-size: 0.9rem;
    }
    
    /* Footer */
    .footer {
        padding: 50px 0 20px;
    }
    
    .footer-brand .logo svg {
        width: 40px;
        height: 40px;
    }
    
    .footer-brand .logo-text {
        font-size: 1.2rem;
    }
    
    .social-link {
        width: 36px;
        height: 36px;
    }
    
    /* Page Header */
    .page-header {
        padding: 130px 15px 50px;
    }
    
    .page-header h1 {
        font-size: 1.8rem;
    }
    
    .page-header p {
        font-size: 0.95rem;
    }
    
    /* Buttons */
    .btn {
        padding: 12px 24px;
        font-size: 0.85rem;
    }
    
    /* Contact Form */
    .contact-grid {
        grid-template-columns: 1fr;
    }
    
    .contact-info {
        order: -1;
        margin-bottom: 30px;
    }
    
    /* Accordion */
    .accordion-header {
        padding: 15px 20px;
        font-size: 1rem;
    }
    
    .accordion-content {
        padding: 15px 20px;
        font-size: 0.9rem;
    }
    
    /* Table */
    .table-container {
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
    }
    
    table {
        font-size: 0.85rem;
    }
    
    th, td {
        padding: 10px 12px;
    }
    
    /* Tabs */
    .tab-buttons {
        flex-wrap: wrap;
        gap: 10px;
    }
    
    .tab-btn {
        padding: 10px 20px;
        font-size: 0.9rem;
        flex: 1 1 auto;
        min-width: 120px;
    }
    
    /* Modal */
    .modal-content {
        padding: 25px 20px;
        margin: 20px;
    }
    
    /* Toast */
    .toast {
        left: 20px;
        right: 20px;
        bottom: 20px;
    }
}

/* Extra Small Devices */
@media (max-width: 375px) {
    .hero-title {
        font-size: 1.8rem;
    }
    
    .section-title {
        font-size: 1.5rem;
    }
    
    .phone-mockup {
        width: 180px;
        height: 360px;
        border-radius: 25px;
    }
    
    .phone-screen {
        border-radius: 20px;
    }
    
    .phone-notch {
        width: 60px;
        height: 20px;
    }
    
    .btn {
        padding: 10px 20px;
        font-size: 0.8rem;
    }
    
    .stat-number {
        font-size: 1.75rem;
    }
}

/* Landscape Mode on Mobile */
@media (max-height: 500px) and (orientation: landscape) {
    .hero {
        min-height: auto;
        padding: 100px 20px 40px;
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .scroll-indicator {
        display: none;
    }
    
    .phone-mockup {
        display: none;
    }
}

/* High DPI Displays */
@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
    /* Crisp rendering for high DPI displays */
    .logo svg,
    .service-image svg,
    .about-card-icon svg {
        shape-rendering: geometricPrecision;
    }
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
    
    .hero-bg::before {
        animation: none;
    }
    
    .particle {
        animation: none;
    }
    
    .scroll-indicator {
        animation: none;
    }
}

/* Dark Mode (System Preference) */
@media (prefers-color-scheme: dark) {
    /* Already dark by default, but can add specific overrides here */
}

/* Print Styles */
@media print {
    .navbar,
    .scroll-indicator,
    .hero-bg-animation,
    .particles,
    .cursor-trail,
    .btn {
        display: none !important;
    }
    
    body {
        background: white;
        color: black;
    }
    
    .section {
        padding: 20px 0;
        page-break-inside: avoid;
    }
    
    a {
        color: black;
        text-decoration: underline;
    }
    
    .footer {
        background: #f5f5f5;
    }
}

/* Touch Device Optimizations */
@media (hover: none) and (pointer: coarse) {
    .nav-links a:hover::after {
        width: 0;
    }
    
    .service-card:hover,
    .about-card:hover,
    .btn:hover {
        transform: none;
    }
    
    /* Remove hover effects on touch devices */
    .hover-card:hover {
        transform: none;
    }
    
    .flip-card:hover .flip-card-inner {
        transform: none;
    }
    
    /* Add active states instead */
    .btn:active {
        transform: scale(0.98);
    }
    
    .service-card:active,
    .about-card:active {
        transform: scale(0.98);
    }
}