/* ==========================================================================
   STYLE SYSTEM - PREMIUM LIGHT THEME (Inter Font)
   Inspired by Apple, Stripe, and Figma
   ========================================================================== */

:root {
    /* Color Palette */
    --bg-base: #F8FAFC;
    --bg-card: #FFFFFF;
    --primary: #2563EB;
    --primary-hover: #1D4ED8;
    --border: #E5E7EB;
    --title: #111827;
    --text: #475569;
    --accent-blue-light: #EFF6FF;
    
    /* Layout */
    --radius-premium: 20px;
    --transition-smooth: all 0.3s cubic-bezier(0.16, 1, 0.3, 1);
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -1px rgba(0, 0, 0, 0.03);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.05), 0 4px 6px -2px rgba(0, 0, 0, 0.03);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.05), 0 10px 10px -5px rgba(0, 0, 0, 0.02);
    --shadow-premium: 0 24px 48px -12px rgba(0, 0, 0, 0.06), 0 4px 12px -4px rgba(0, 0, 0, 0.02);
}

/* ==========================================================================
   BASE & RESET
   ========================================================================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-family: var(--font-sans);
    background-color: var(--bg-base);
    color: var(--text);
    overflow-x: hidden;
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}

body {
    min-height: 100vh;
    background-color: var(--bg-base);
}

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

.section-padding {
    padding: 120px 0;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    color: var(--title);
    font-weight: 700;
    letter-spacing: -0.025em;
    line-height: 1.2;
}

p {
    font-size: 1rem;
    font-weight: 400;
    line-height: 1.6;
}

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

/* ==========================================================================
   PRELOADER
   ========================================================================== */
.loader {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: var(--bg-base);
    z-index: 9999;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: opacity 0.5s ease, visibility 0.5s;
}

.loader-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 16px;
}

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid rgba(37, 99, 235, 0.1);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

.loader-logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--title);
    letter-spacing: -0.03em;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* ==========================================================================
   STICKY HEADER / NAVBAR
   ========================================================================== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 1000;
    background: transparent;
    border-bottom: 1px solid transparent;
    transition: var(--transition-smooth);
    padding: 20px 0;
}

.navbar.scrolled {
    padding: 12px 0;
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--border);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.02);
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    color: var(--title);
    text-decoration: none;
    font-weight: 700;
    font-size: 1.25rem;
    letter-spacing: -0.03em;
}

.web-logo {
    height: 32px;
    width: auto;
    object-fit: contain;
    border-radius: 6px;
    transition: var(--transition-smooth);
}

.nav-logo:hover .web-logo {
    transform: scale(1.05);
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 32px;
}

.nav-link {
    color: var(--text);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    transition: var(--transition-smooth);
    padding: 8px 0;
}

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

.nav-actions {
    display: flex;
    align-items: center;
    gap: 16px;
}

.nav-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--title);
    font-size: 1.25rem;
    cursor: pointer;
    padding: 8px;
    transition: var(--transition-smooth);
}

/* ==========================================================================
   BUTTONS
   ========================================================================== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 20px;
    border-radius: 8px;
    font-size: 0.95rem;
    font-weight: 600;
    text-decoration: none;
    transition: var(--transition-smooth);
    border: 1px solid transparent;
    cursor: pointer;
}

.btn-primary {
    background-color: var(--primary);
    color: #FFFFFF;
    box-shadow: 0 1px 2px rgba(37, 99, 235, 0.05);
}

.btn-primary:hover {
    background-color: var(--primary-hover);
    transform: translateY(-1px);
}

.btn-secondary {
    background-color: var(--bg-card);
    color: var(--text);
    border-color: var(--border);
    box-shadow: var(--shadow-sm);
}

.btn-secondary:hover {
    background-color: #F8FAFC;
    color: var(--title);
    border-color: #D1D5DB;
    transform: translateY(-1px);
}

.btn-nav {
    padding: 8px 16px;
    font-size: 0.9rem;
    background-color: var(--primary);
    color: #FFFFFF;
}

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

/* ==========================================================================
   HERO SECTION
   ========================================================================== */
.hero-section {
    padding-top: 180px;
    padding-bottom: 120px;
    background: radial-gradient(circle at 80% 20%, rgba(37, 99, 235, 0.04), transparent 50%),
                radial-gradient(circle at 10% 70%, rgba(37, 99, 235, 0.02), transparent 40%);
}

.hero-container {
    display: grid;
    grid-template-columns: 1.1fr 0.9fr;
    gap: 60px;
    align-items: center;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    background-color: var(--accent-blue-light);
    border: 1px solid rgba(37, 99, 235, 0.15);
    padding: 6px 14px;
    border-radius: 9999px;
    margin-bottom: 24px;
}

.badge-dot {
    width: 6px;
    height: 6px;
    background-color: var(--primary);
    border-radius: 50%;
}

.badge-text {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--primary);
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 800;
    line-height: 1.1;
    color: var(--title);
    margin-bottom: 20px;
    letter-spacing: -0.035em;
}

.hero-description {
    font-size: 1.125rem;
    color: var(--text);
    margin-bottom: 36px;
    line-height: 1.6;
}

.hero-cta {
    display: flex;
    gap: 16px;
}

.hero-cta .btn {
    padding: 14px 28px;
    border-radius: 10px;
    font-size: 1rem;
}

/* Floating Laptop Mockup */
.hero-visual-side {
    display: flex;
    justify-content: center;
    position: relative;
}

.laptop-mockup-wrapper {
    position: relative;
    width: 100%;
    max-width: 520px;
    perspective: 1000px;
    animation: floatLaptop 6s ease-in-out infinite;
}

.laptop-screen {
    background: #000;
    border-radius: 16px 16px 0 0;
    padding: 10px 10px 0 10px;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.12);
    border: 4px solid #1E293B;
    border-bottom: none;
}

.laptop-screen-img {
    width: 100%;
    height: auto;
    border-radius: 8px 8px 0 0;
    display: block;
    object-fit: cover;
}

.laptop-base {
    height: 12px;
    background: #E2E8F0;
    border-radius: 0 0 12px 12px;
    position: relative;
    box-shadow: 0 20px 40px -10px rgba(0, 0, 0, 0.1);
    border-top: 1px solid #CBD5E1;
}

.laptop-base::after {
    content: '';
    position: absolute;
    width: 80px;
    height: 4px;
    background: #94A3B8;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
    border-radius: 0 0 4px 4px;
}

@keyframes floatLaptop {
    0% { transform: translateY(0px); }
    50% { transform: translateY(-10px); }
    100% { transform: translateY(0px); }
}

/* ==========================================================================
   SECTIONS GENERAL
   ========================================================================== */
.section-header {
    margin-bottom: 72px;
}

.section-title {
    font-size: 2.25rem;
    font-weight: 800;
    color: var(--title);
    margin-bottom: 16px;
    letter-spacing: -0.03em;
}

.section-subtitle {
    font-size: 1.1rem;
    color: var(--text);
    max-width: 600px;
    margin: 0 auto;
    line-height: 1.6;
}

/* ==========================================================================
   ALTERNATING FEATURES SECTION
   ========================================================================== */
.features-list {
    display: flex;
    flex-direction: column;
    gap: 96px;
}

.feature-item {
    display: flex;
    align-items: center;
    gap: 80px;
}

.feature-item.reverse {
    flex-direction: row-reverse;
}

.feature-content {
    flex: 1;
}

.feature-visual {
    flex: 1;
    display: flex;
    justify-content: center;
}

.feature-icon-wrapper {
    width: 48px;
    height: 48px;
    background-color: var(--accent-blue-light);
    color: var(--primary);
    border-radius: 12px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.25rem;
    margin-bottom: 24px;
}

.feature-item-title {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--title);
    margin-bottom: 16px;
}

.feature-item-description {
    font-size: 1.05rem;
    color: var(--text);
    line-height: 1.7;
}

.feature-img-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-premium);
    padding: 12px;
    box-shadow: var(--shadow-premium);
    transition: var(--transition-smooth);
    width: 100%;
    max-width: 520px;
}

.feature-img-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 30px 60px -15px rgba(0, 0, 0, 0.08);
}

.feature-img {
    width: 100%;
    height: auto;
    border-radius: 12px;
    display: block;
    object-fit: cover;
}

/* ==========================================================================
   SCREENSHOTS SECTION
   ========================================================================== */
.screenshots-section {
    background-color: #FFFFFF;
    border-top: 1px solid var(--border);
    border-bottom: 1px solid var(--border);
}

.gallery-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.gallery-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-premium);
    overflow: hidden;
    box-shadow: var(--shadow-md);
    transition: var(--transition-smooth);
}

.gallery-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-premium);
    border-color: rgba(37, 99, 235, 0.2);
}

.gallery-img-container {
    position: relative;
    overflow: hidden;
    aspect-ratio: 16/10;
    cursor: zoom-in;
    background-color: var(--bg-base);
    border-bottom: 1px solid var(--border);
}

.gallery-img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
    transition: var(--transition-smooth);
}

.gallery-card:hover .gallery-img {
    transform: scale(1.03);
}

.gallery-info {
    padding: 24px;
}

.gallery-info h4 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--title);
    margin-bottom: 6px;
}

.gallery-info p {
    font-size: 0.9rem;
    color: var(--text);
}

/* ==========================================================================
   LIGHTBOX MODAL
   ========================================================================== */
.lightbox {
    display: none;
    position: fixed;
    z-index: 2000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(248, 250, 252, 0.95);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    justify-content: center;
    align-items: center;
}

.lightbox-wrapper {
    position: relative;
    max-width: 85%;
    max-height: 80%;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.lightbox-content {
    max-width: 100%;
    max-height: 70vh;
    object-fit: contain;
    border-radius: 12px;
    box-shadow: var(--shadow-xl);
    border: 1px solid var(--border);
    animation: lightboxZoom 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

@keyframes lightboxZoom {
    from { transform: scale(0.95); opacity: 0; }
    to { transform: scale(1); opacity: 1; }
}

.lightbox-close {
    position: absolute;
    top: -50px;
    right: 0;
    background: none;
    border: none;
    color: var(--title);
    font-size: 2.5rem;
    cursor: pointer;
    line-height: 1;
    transition: var(--transition-smooth);
}

.lightbox-close:hover {
    color: var(--primary);
}

.lightbox-caption {
    margin-top: 16px;
    font-size: 1rem;
    font-weight: 500;
    color: var(--title);
}

/* ==========================================================================
   WHY CHOOSE SECTION
   ========================================================================== */
.why-choose-section {
    background-color: #EEF2F6; /* Section nền xanh rất nhạt */
}

.why-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 30px;
}

.why-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-premium);
    padding: 40px;
    box-shadow: var(--shadow-sm);
    transition: var(--transition-smooth);
}

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

.why-icon-box {
    width: 48px;
    height: 48px;
    border-radius: 12px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.25rem;
    margin-bottom: 24px;
}

.why-icon-box.blue { background-color: #EFF6FF; color: #2563EB; }
.why-icon-box.green { background-color: #ECFDF5; color: #10B981; }
.why-icon-box.purple { background-color: #F5F3FF; color: #8B5CF6; }
.why-icon-box.orange { background-color: #FFF7ED; color: #F97316; }

.why-card h4 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--title);
    margin-bottom: 12px;
}

.why-card p {
    font-size: 0.95rem;
    color: var(--text);
    line-height: 1.6;
}

/* ==========================================================================
   DOWNLOAD SECTION
   ========================================================================== */
.download-container {
    max-width: 900px;
    margin: 0 auto;
}

.download-main-card {
    background: linear-gradient(135deg, #FFFFFF 0%, #F1F5F9 100%);
    border: 1px solid var(--border);
    border-radius: 24px;
    padding: 60px;
    text-align: center;
    box-shadow: var(--shadow-premium);
    position: relative;
    overflow: hidden;
}

.download-badge {
    display: inline-block;
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--primary);
    background-color: var(--accent-blue-light);
    border: 1px solid rgba(37, 99, 235, 0.15);
    padding: 6px 16px;
    border-radius: 9999px;
    margin-bottom: 24px;
}

.download-title {
    font-size: 2.25rem;
    font-weight: 800;
    margin-bottom: 12px;
}

.download-subtitle {
    font-size: 1.05rem;
    color: var(--text);
    margin-bottom: 40px;
}

.download-action-box {
    margin-bottom: 48px;
}

.btn-download-primary {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    background-color: var(--primary);
    color: #FFFFFF;
    padding: 16px 36px;
    border-radius: 12px;
    font-size: 1.1rem;
    font-weight: 600;
    text-decoration: none;
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.15);
    transition: var(--transition-smooth);
}

.btn-download-primary:hover {
    background-color: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(37, 99, 235, 0.25);
}

.download-details-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
    border-top: 1px solid var(--border);
    border-bottom: 1px solid var(--border);
    padding: 32px 0;
    margin-bottom: 32px;
}

.detail-item {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.detail-label {
    font-size: 0.85rem;
    color: var(--text);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.detail-value {
    font-size: 1rem;
    font-weight: 600;
    color: var(--title);
}

.sha-box {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
}

.sha-label {
    font-size: 0.85rem;
    color: var(--text);
}

.sha-code {
    font-family: SFMono-Regular, Consolas, "Liberation Mono", Menlo, monospace;
    font-size: 0.85rem;
    background-color: #E2E8F0;
    color: #0F172A;
    padding: 6px 12px;
    border-radius: 6px;
    border: 1px solid var(--border);
    max-width: 100%;
    word-break: break-all;
}

/* ==========================================================================
   FAQ SECTION (ACCORDION)
   ========================================================================== */
.faq-section {
    background-color: #FFFFFF;
    border-top: 1px solid var(--border);
    border-bottom: 1px solid var(--border);
}

.faq-accordion {
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.accordion-item {
    background-color: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 14px;
    overflow: hidden;
    transition: var(--transition-smooth);
}

.accordion-header {
    width: 100%;
    background: none;
    border: none;
    text-align: left;
    padding: 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
}

.accordion-header h3 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--title);
    padding-right: 20px;
}

.accordion-header .icon {
    font-size: 1rem;
    color: var(--text);
    transition: var(--transition-smooth);
}

.accordion-body {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s cubic-bezier(0.16, 1, 0.3, 1), padding 0.3s ease;
    padding: 0 24px;
}

.accordion-body p {
    font-size: 0.95rem;
    color: var(--text);
    line-height: 1.6;
    padding-bottom: 24px;
}

/* Active State */
.accordion-item.active {
    border-color: rgba(37, 99, 235, 0.3);
    box-shadow: var(--shadow-md);
}

.accordion-item.active .accordion-header .icon {
    transform: rotate(45deg);
    color: var(--primary);
}

/* ==========================================================================
   CONTACT SECTION
   ========================================================================== */
.contact-container {
    max-width: 900px;
    margin: 0 auto;
}

.contact-main-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-premium);
    padding: 60px;
    text-align: center;
    box-shadow: var(--shadow-premium);
}

.contact-title {
    font-size: 2.25rem;
    font-weight: 800;
    margin-bottom: 12px;
}

.contact-subtitle {
    font-size: 1.05rem;
    color: var(--text);
    margin-bottom: 48px;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.contact-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
}

.contact-item-card {
    background-color: var(--bg-base);
    border: 1px solid var(--border);
    border-radius: 16px;
    padding: 24px 16px;
    display: flex;
    flex-direction: column;
    align-items: center;
    text-decoration: none;
    color: var(--text);
    transition: var(--transition-smooth);
}

.contact-item-card:hover {
    background-color: #FFFFFF;
    border-color: rgba(37, 99, 235, 0.25);
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

.contact-icon {
    width: 44px;
    height: 44px;
    background-color: #FFFFFF;
    border: 1px solid var(--border);
    border-radius: 10px;
    display: flex;
    justify-content: center;
    align-items: center;
    color: var(--text);
    font-size: 1.15rem;
    margin-bottom: 16px;
    transition: var(--transition-smooth);
}

.contact-item-card:hover .contact-icon {
    color: var(--primary);
    border-color: rgba(37, 99, 235, 0.2);
    box-shadow: var(--shadow-sm);
}

.contact-label {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text);
    margin-bottom: 4px;
}

.contact-value {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--title);
}

/* ==========================================================================
   FOOTER SECTION
   ========================================================================== */
.footer {
    background-color: #FFFFFF;
    border-top: 1px solid var(--border);
    padding: 48px 0;
}

.footer-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

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

.web-logo-footer {
    height: 28px;
    width: auto;
    object-fit: contain;
    filter: opacity(0.85);
}

.footer-meta {
    display: flex;
    gap: 32px;
    font-size: 0.9rem;
    color: var(--text);
}

/* ==========================================================================
   ANIMATIONS (SCROLL REVEAL OBSERVER)
   ========================================================================== */
.reveal-slide-up {
    opacity: 0;
    transform: translateY(24px);
    transition: opacity 0.8s cubic-bezier(0.16, 1, 0.3, 1), transform 0.8s cubic-bezier(0.16, 1, 0.3, 1);
}

.reveal-slide-up.animated {
    opacity: 1;
    transform: translateY(0);
}

.reveal-fade {
    opacity: 0;
    transition: opacity 1s cubic-bezier(0.16, 1, 0.3, 1);
}

.reveal-fade.animated {
    opacity: 1;
}

/* Delay for staggered visual appearance */
.gallery-card:nth-child(1) { transition-delay: 0s; }
.gallery-card:nth-child(2) { transition-delay: 0.05s; }
.gallery-card:nth-child(3) { transition-delay: 0.1s; }

.why-card:nth-child(1) { transition-delay: 0s; }
.why-card:nth-child(2) { transition-delay: 0.05s; }
.why-card:nth-child(3) { transition-delay: 0.1s; }
.why-card:nth-child(4) { transition-delay: 0.15s; }