/* === Premium CSS Variables === */
:root {
    --color-black: #0a0a0a; 
    --color-dark: #171717;
    --color-grey-dark: #52525b;
    --color-grey-light: #a1a1aa;
    --color-bg-light: #f9fafb;
    --color-white: #ffffff;
    --color-border: rgba(0, 0, 0, 0.08);

    /* Brand accent: indigo — threads through hero gradients, buttons & interactive elements */
    --color-brand: #6366f1;
    --color-brand-dark: #4f46e5;
    --color-brand-deeper: #4338ca;
    --color-brand-bg: rgba(99, 102, 241, 0.08);
    --color-brand-border: rgba(99, 102, 241, 0.25);
    --shadow-brand: 0 12px 28px rgba(99, 102, 241, 0.35);

    --font-en: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-cn: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
    --transition: all 0.5s cubic-bezier(0.16, 1, 0.3, 1);
    
    /* Diffusion shadows used by major tech companies */
    --shadow-sm: 0 4px 12px rgba(0, 0, 0, 0.03);
    --shadow-card: 0 12px 32px -4px rgba(0, 0, 0, 0.08), 0 4px 12px -2px rgba(0, 0, 0, 0.04);
    --shadow-float: 0 32px 64px -12px rgba(0, 0, 0, 0.14);
}

/* === Reset & Base Typography === */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    overflow-x: hidden;
}

body {
    font-family: var(--font-cn);
    color: var(--color-grey-dark);
    line-height: 1.8;
    background-color: var(--color-white);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-en);
    color: var(--color-black);
    line-height: 1.15;
}

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

ul {
    list-style: none;
}

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

/* === Layout Utilities === */
.container {
    width: 100%;
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 32px;
}

.section-pd {
    padding: 140px 0;
}

/* === Buttons === */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 15px 36px;
    border-radius: 60px;
    font-weight: 500;
    font-size: 0.95rem;
    cursor: pointer;
    transition: var(--transition);
    border: 1px solid transparent;
    letter-spacing: 0.5px;
}

.btn-white {
    background-color: rgba(255, 255, 255, 0.98);
    color: var(--color-black);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
}

.btn-white:hover {
    background-color: var(--color-white);
    transform: translateY(-2px) scale(1.02);
    box-shadow: 0 12px 30px rgba(255, 255, 255, 0.15);
}

.btn-black {
    background: linear-gradient(135deg, var(--color-brand-dark) 0%, var(--color-brand) 100%);
    color: var(--color-white);
    border: 1px solid var(--color-brand-border);
}

.btn-black:hover {
    background: linear-gradient(135deg, var(--color-brand-deeper) 0%, var(--color-brand-dark) 100%);
    box-shadow: var(--shadow-brand);
    transform: translateY(-2px);
}

.btn-outline {
    background-color: transparent;
    color: var(--color-black);
    border: 1px solid rgba(255, 255, 255, 0.3);
}

.btn-outline:hover {
    background-color: rgba(255, 255, 255, 0.1);
    border-color: var(--color-white);
    transform: translateY(-2px);
}

/* Hero: outline button sits on dark overlay — black text is invisible */
.hero .btn-outline {
    color: var(--color-white);
}

.hero .btn-outline:hover {
    color: var(--color-white);
}

/* High-contrast subtitle: very wide letter-spacing, very small font size */
.subtitle-label {
    font-family: var(--font-en);
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.25em;
    color: var(--color-grey-light);
    font-weight: 600;
    margin-bottom: 20px;
    display: block;
}

/* === Header === */
header {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 100;
    padding: 24px 0;
    border-bottom: 1px solid rgba(255, 255, 255, 0.08);
    transition: var(--transition);
}

header.sticky {
    position: fixed;
    background-color: rgba(255, 255, 255, 0.8);
    backdrop-filter: saturate(180%) blur(20px);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
    border-bottom: 1px solid var(--color-border);
    padding: 16px 0;
    box-shadow: 0 4px 30px rgba(0, 0, 0, 0.02);
}

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

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
    font-family: var(--font-en);
    font-size: 1.4rem;
    font-weight: 800;
    color: var(--color-white);
    letter-spacing: -0.05em;
}

header.sticky .logo { color: var(--color-black); }
.logo i { font-size: 1.6rem; }
.logo-img { width: 36px; height: 36px; object-fit: contain; }

.nav-menu {
    display: flex;
    gap: 48px;
}

.nav-menu a {
    color: rgba(255, 255, 255, 0.8);
    font-weight: 500;
    font-size: 0.9rem;
    letter-spacing: 0.5px;
}

header.sticky .nav-menu a { color: var(--color-grey-dark); }
header.sticky .nav-menu a:hover { color: var(--color-black); }
.nav-menu a:hover { opacity: 1; color: var(--color-white); }

.nav-menu a.active {
    color: var(--color-white);
    opacity: 1;
    position: relative;
}
.nav-menu a.active::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--color-white);
    border-radius: 2px;
}
header.sticky .nav-menu a.active { color: var(--color-black); font-weight: 600; }
header.sticky .nav-menu a.active::after { background: var(--color-black); }

.nav-right {
    display: flex;
    align-items: center;
    gap: 24px;
}

.lang-dropdown {
    position: relative;
}

.lang-toggle {
    color: var(--color-white);
    display: flex;
    align-items: center;
    gap: 6px;
    cursor: pointer;
    font-size: 0.85rem;
    font-weight: 600;
    letter-spacing: 0.5px;
    opacity: 0.8;
    background: none;
    border: none;
    padding: 0;
    font-family: var(--font-en);
    transition: var(--transition);
}
.lang-toggle:hover { opacity: 1; }
header.sticky .lang-toggle { color: var(--color-grey-dark); }

.lang-arrow {
    font-size: 0.6rem;
    transition: transform 0.25s ease;
}

.lang-dropdown.open .lang-arrow {
    transform: rotate(180deg);
}

/* === Language Dropdown Panel === */
.lang-menu {
    position: absolute;
    top: calc(100% + 14px);
    right: 0;
    min-width: 180px;
    background: #ffffff;
    border: 1px solid rgba(0, 0, 0, 0.07);
    border-radius: 16px;
    padding: 6px;
    box-shadow: 0 20px 60px -12px rgba(0, 0, 0, 0.18), 0 4px 16px rgba(0, 0, 0, 0.06);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-6px) scale(0.97);
    transform-origin: top right;
    transition: opacity 0.2s ease, transform 0.2s ease, visibility 0.2s;
    z-index: 200;
}

.lang-dropdown.open .lang-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0) scale(1);
}

.lang-option {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 14px;
    border-radius: 10px;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-grey-dark);
    transition: background 0.15s, color 0.15s;
    cursor: pointer;
    white-space: nowrap;
    line-height: 1;
}

.lang-option:hover {
    background: var(--color-bg-light);
    color: var(--color-black);
}

.lang-option.active {
    color: var(--color-black);
    font-weight: 600;
    background: var(--color-bg-light);
}

.lang-flag {
    font-size: 1rem;
    line-height: 1;
    flex-shrink: 0;
}

.btn-header {
    padding: 10px 24px;
    border-radius: 50px;
    background: rgba(255, 255, 255, 0.08);
    color: var(--color-white);
    font-weight: 500;
    font-size: 0.85rem;
    border: 1px solid rgba(255, 255, 255, 0.15);
    transition: var(--transition);
}

header.sticky .btn-header {
    background: linear-gradient(135deg, var(--color-brand-dark) 0%, var(--color-brand) 100%);
    color: var(--color-white);
    border-color: var(--color-brand-border);
}

.btn-header:hover { 
    background: var(--color-white); 
    color: var(--color-brand-dark); 
    transform: translateY(-1px); 
}

header.sticky .btn-header:hover {
    background: linear-gradient(135deg, var(--color-brand-deeper) 0%, var(--color-brand-dark) 100%);
    box-shadow: var(--shadow-brand);
    color: var(--color-white);
}

.mobile-menu-btn { display: none; color: var(--color-white); font-size: 1.4rem; cursor: pointer; }
header.sticky .mobile-menu-btn { color: var(--color-black); }

/* === Hero Section === */
.hero {
    position: relative;
    height: 100vh;
    min-height: 850px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: url('../images/download-bg.jpg') center/cover no-repeat;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0; left: 0; width: 100%; height: 100%;
    background: linear-gradient(135deg, rgba(9, 9, 11, 0.88) 0%, rgba(15, 14, 40, 0.55) 100%);
}

.hero::after {
    content: '';
    position: absolute;
    top: -50%; left: -50%;
    width: 200%; height: 200%;
    background:
        radial-gradient(ellipse at 20% 60%, rgba(99, 102, 241, 0.12) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 30%, rgba(79, 70, 229, 0.08) 0%, transparent 45%);
    pointer-events: none;
}

.hero-content {
    position: relative;
    z-index: 10;
    text-align: center;
    max-width: 900px;
    padding: 0 20px;
}

.hero-label {
    display: inline-block;
    color: rgba(255, 255, 255, 0.7);
    text-transform: uppercase;
    letter-spacing: 4px;
    font-size: 0.75rem;
    margin-bottom: 30px;
    font-weight: 600;
    border: 1px solid rgba(255,255,255,0.1);
    padding: 6px 16px;
    border-radius: 30px;
    backdrop-filter: blur(4px);
}

.hero h1 {
    color: var(--color-white);
    font-size: 5rem;
    font-weight: 800;
    letter-spacing: -0.04em;
    line-height: 1.05;
    margin-bottom: 32px;
    text-shadow: 0 20px 40px rgba(0,0,0,0.5);
}

.hero p {
    color: rgba(255, 255, 255, 0.7);
    font-size: 1.25rem;
    margin-bottom: 48px;
    max-width: 650px;
    margin-left: auto;
    margin-right: auto;
    font-weight: 400;
    line-height: 1.6;
}

/* Decorative Arrows */
.hero-arrow {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: rgba(255,255,255,0.03);
    border: 1px solid rgba(255,255,255,0.1);
    color: rgba(255,255,255,0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    z-index: 10;
    backdrop-filter: blur(10px);
    transition: var(--transition);
}
.hero-arrow:hover { 
    background: rgba(255,255,255,0.1); 
    color: white;
    border-color: rgba(255,255,255,0.3);
}
.hero-arrow.left { left: 40px; }
.hero-arrow.right { right: 40px; }

/* === Section 2: Trust & Overview === */
.overview { background-color: var(--color-white); }

.overview-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 100px;
    align-items: center;
}

/* Left Image Composition */
.image-composition {
    position: relative;
    width: 100%;
    padding-right: 40px;
    padding-bottom: 40px;
}

.img-main {
    width: 90%;
    border-radius: 24px;
    box-shadow: var(--shadow-float);
    transition: var(--transition);
}

.img-sub {
    position: absolute;
    right: -10px;
    bottom: -10px;
    width: 55%;
    border-radius: 20px;
    border: 10px solid var(--color-white);
    box-shadow: var(--shadow-float);
    z-index: 2;
    transition: var(--transition);
}

.image-composition:hover .img-main { transform: scale(1.01) translateY(-4px); }
.image-composition:hover .img-sub { transform: translateY(-12px) scale(1.03); z-index: 4; }

/* Floating Dark Data Card */
.data-card {
    position: absolute;
    top: 50px;
    left: -40px;
    background: rgba(15, 15, 17, 0.85);
    color: var(--color-white);
    padding: 32px 40px;
    border-radius: 20px;
    z-index: 3;
    box-shadow: 0 32px 64px rgba(0,0,0,0.2);
    border: 1px solid rgba(255, 255, 255, 0.1);
    backdrop-filter: saturate(180%) blur(20px);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
    transition: var(--transition);
}

.data-card:hover {
    transform: translateY(-8px);
}

.data-card h3 {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 2px;
    letter-spacing: -0.05em;
    background: linear-gradient(135deg, #ffffff 0%, #a1a1aa 100%);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.data-card p {
    font-size: 0.85rem;
    color: rgba(255,255,255,0.6);
    line-height: 1.5;
    letter-spacing: 0.5px;
}

/* Right Content */
.overview-content h2 {
    font-size: 3.2rem;
    margin-bottom: 28px;
    letter-spacing: -0.03em;
    color: var(--color-black);
}

.overview-content > p {
    font-size: 1.15rem;
    margin-bottom: 40px;
    color: var(--color-grey-dark);
    line-height: 1.8;
}

.check-list { margin-bottom: 48px; }
.check-list li {
    display: flex;
    align-items: center;
    gap: 16px;
    margin-bottom: 20px;
    font-size: 1.05rem;
    font-weight: 500;
    color: #27272a;
}
.check-list i { color: #10b981; font-size: 1.2rem; background: rgba(16, 185, 129, 0.1); border-radius: 50%; padding: 4px; }

.signature { margin-top: 30px; height: 50px; opacity: 0.4; mix-blend-mode: multiply; }

.overview-actions {
    display: flex;
    align-items: center;
    gap: 32px;
}

.contact-info {
    display: flex;
    align-items: center;
    gap: 14px;
}
.contact-icon {
    width: 48px; height: 48px;
    background: var(--color-brand-bg);
    border: 1px solid var(--color-brand-border);
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    color: var(--color-brand);
    font-size: 1.1rem;
}

/* === Section 3: Core Features === */
.features { background-color: var(--color-bg-light); }

.section-header { text-align: center; margin-bottom: 80px; }
.section-header h2 { font-size: 2.8rem; letter-spacing: -0.03em; }

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 32px;
}

.feature-card {
    display: flex;
    flex-direction: column;
    height: 100%;
    background: var(--color-white);
    padding: 56px 48px;
    border-radius: 24px;
    border: 1px solid var(--color-border);
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

.feature-card:hover {
    box-shadow: var(--shadow-card);
    transform: translateY(-10px);
    border-color: rgba(0, 0, 0, 0.12);
}

.f-icon-wrapper {
    width: 64px; height: 64px;
    background: var(--color-brand-bg);
    border-radius: 16px;
    display: flex; align-items: center; justify-content: center;
    margin-bottom: 32px;
    border: 1px solid var(--color-brand-border);
    transition: var(--transition);
}

.feature-card:hover .f-icon-wrapper {
    background: linear-gradient(135deg, var(--color-brand-dark) 0%, var(--color-brand) 100%);
    border-color: transparent;
}

.f-icon {
    font-size: 1.8rem;
    color: var(--color-brand);
    transition: var(--transition);
}

.feature-card:hover .f-icon {
    color: var(--color-white);
}

.feature-card h3 {
    font-size: 1.5rem;
    margin-bottom: 16px;
    letter-spacing: -0.02em;
}

.feature-card p {
    flex: 1 1 auto;
    font-size: 1rem;
    margin-bottom: 0;
    color: var(--color-grey-dark);
    line-height: 1.7;
}

.f-link {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    margin-top: 36px;
    font-weight: 600;
    color: var(--color-brand);
    font-size: 0.9rem;
    letter-spacing: 0.5px;
    transition: var(--transition);
}

.f-link:hover { color: var(--color-brand-dark); }

.f-link i {
    width: 36px; height: 36px;
    background: var(--color-brand-bg);
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    transition: var(--transition);
    border: 1px solid var(--color-brand-border);
    color: var(--color-brand);
}

.feature-card:hover .f-link i {
    background: var(--color-brand);
    color: var(--color-white);
    border-color: var(--color-brand);
    transform: translateX(4px);
}

/* === Section 4: Banner CTA === */
.banner-cta {
    background: url('../images/docs-bg.jpg') center/cover fixed;
    position: relative;
    padding: 120px 0;
}

.banner-cta::before {
    content: '';
    position: absolute;
    top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(10, 10, 12, 0.88);
    backdrop-filter: blur(2px);
}

.banner-container {
    position: relative;
    z-index: 10;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.banner-text h2 {
    color: var(--color-white);
    font-size: 3rem;
    max-width: 650px;
    line-height: 1.25;
    letter-spacing: -0.03em;
}

/* === Section 5: Platforms === */
.platforms { background-color: var(--color-white); }

.platform-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 100px;
    align-items: center;
}

.platform-content h2 {
    font-size: 3rem;
    margin-bottom: 32px;
    letter-spacing: -0.03em;
}

.platform-item {
    display: flex;
    gap: 24px;
    margin-bottom: 40px;
    padding: 20px;
    border-radius: 20px;
    transition: var(--transition);
    border: 1px solid transparent;
}

.platform-item:hover {
    background: var(--color-bg-light);
    border-color: var(--color-border);
}

.platform-icon {
    width: 64px; height: 64px;
    background: var(--color-brand-bg);
    border: 1px solid var(--color-brand-border);
    border-radius: 16px;
    display: flex; align-items: center; justify-content: center;
    font-size: 1.8rem;
    color: var(--color-brand);
    flex-shrink: 0;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.platform-item:hover .platform-icon {
    background: linear-gradient(135deg, var(--color-brand-dark) 0%, var(--color-brand) 100%);
    border-color: transparent;
    color: var(--color-white);
    box-shadow: 0 8px 20px rgba(99, 102, 241, 0.28);
}

.platform-text h4 { font-size: 1.25rem; margin-bottom: 10px; }
.platform-text p { font-size: 1rem; color: var(--color-grey-dark); }

.platform-images {
    position: relative;
    height: 650px;
    border-radius: 32px;
}

.p-img-1 { 
    position: absolute; top: 0; left: 0; width: 75%; 
    border-radius: 24px; box-shadow: var(--shadow-float); transition: var(--transition); 
}
.p-img-2 { 
    position: absolute; bottom: 0; right: 0; width: 55%; 
    border-radius: 24px; box-shadow: var(--shadow-float); transition: var(--transition); 
    border: 8px solid var(--color-white);
}

.p-img-1:hover { transform: translateY(-8px) scale(1.02); z-index: 10; }
.p-img-2:hover { transform: translateY(-8px) scale(1.02); z-index: 10; }

/* === Footer === */
footer {
    background-color: var(--color-black);
    color: rgba(255, 255, 255, 0.5);
    padding: 100px 0 40px;
    font-size: 0.95rem;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2.5fr 1fr 1fr 1fr;
    gap: 60px;
    margin-bottom: 80px;
}

.f-logo { color: var(--color-white); margin-bottom: 24px; display: inline-flex; align-items: center; }
.footer-about p { margin-bottom: 32px; max-width: 340px; line-height: 1.8; }

.social-icons { display: flex; gap: 16px; }
.social-icons a {
    width: 44px; height: 44px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.05);
    display: flex; align-items: center; justify-content: center;
    color: var(--color-white);
    border: 1px solid rgba(255,255,255,0.05);
    transition: var(--transition);
}
.social-icons a:hover { 
    background: var(--color-white); 
    color: var(--color-black); 
    transform: translateY(-3px); 
}

.footer-col h4 { color: var(--color-white); font-size: 1rem; margin-bottom: 30px; letter-spacing: 1px; font-weight: 600; }
.footer-col ul li { margin-bottom: 16px; }
.footer-col ul a { transition: color 0.3s ease; }
.footer-col ul a:hover { color: var(--color-white); }

.footer-bottom {
    padding-top: 40px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.85rem;
}

/* Footer language dropdown — opens upward, white text on dark bg */
.footer-lang-dropdown .lang-menu {
    top: auto;
    bottom: calc(100% + 14px);
    transform-origin: bottom right;
    transform: translateY(6px) scale(0.97);
}
.footer-lang-dropdown.open .lang-menu {
    transform: translateY(0) scale(1);
}
.footer-lang-toggle {
    color: rgba(255, 255, 255, 0.7);
}
.footer-lang-toggle:hover {
    color: var(--color-white);
    opacity: 1;
}

/* === Section: Stats Trust Bar === */
.stats-bar {
    background-color: var(--color-black);
    padding: 48px 0;
    border-bottom: 1px solid rgba(255,255,255,0.06);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0;
}

.stat-item {
    text-align: center;
    padding: 20px;
    border-right: 1px solid rgba(255,255,255,0.08);
}

.stat-item:last-child { border-right: none; }

.stat-item .stat-num {
    font-family: var(--font-en);
    font-size: 2.8rem;
    font-weight: 800;
    letter-spacing: -0.04em;
    color: var(--color-white);
    display: block;
    line-height: 1.1;
    margin-bottom: 8px;
}

.stat-item .stat-label {
    font-size: 0.85rem;
    color: rgba(255,255,255,0.45);
    letter-spacing: 0.5px;
}

/* === Section: How It Works === */
.how-it-works { background-color: var(--color-bg-light); }

.steps-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 40px;
    position: relative;
}

.steps-grid::before {
    content: '';
    position: absolute;
    top: 40px;
    left: calc(16.67% + 20px);
    right: calc(16.67% + 20px);
    height: 1px;
    background: linear-gradient(90deg, var(--color-border) 0%, rgba(0,0,0,0.15) 50%, var(--color-border) 100%);
    z-index: 0;
}

.step-card {
    text-align: center;
    padding: 48px 32px;
    position: relative;
    background: var(--color-white);
    border-radius: 24px;
    border: 1px solid var(--color-border);
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

.step-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-card);
    border-color: rgba(0,0,0,0.12);
}

.step-number {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--color-brand-dark) 0%, var(--color-brand) 100%);
    color: var(--color-white);
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: var(--font-en);
    font-size: 1.8rem;
    font-weight: 800;
    margin: 0 auto 28px;
    position: relative;
    z-index: 1;
    box-shadow: 0 8px 24px rgba(99, 102, 241, 0.3);
}

.step-card h3 {
    font-size: 1.35rem;
    margin-bottom: 14px;
    letter-spacing: -0.02em;
}

.step-card p {
    font-size: 1rem;
    color: var(--color-grey-dark);
    line-height: 1.7;
}

/* === Section: FAQ === */
.faq { background-color: var(--color-white); }

.faq-layout {
    display: grid;
    grid-template-columns: 1fr 1.6fr;
    gap: 100px;
    align-items: start;
}

.faq-left h2 {
    font-size: 3rem;
    letter-spacing: -0.03em;
    margin-bottom: 24px;
}

.faq-left p {
    font-size: 1.1rem;
    color: var(--color-grey-dark);
    line-height: 1.8;
    margin-bottom: 40px;
}

.faq-item {
    border-bottom: 1px solid var(--color-border);
}

.faq-item:first-child {
    border-top: 1px solid var(--color-border);
}

.faq-question {
    width: 100%;
    background: none;
    border: none;
    text-align: left;
    padding: 28px 0;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    gap: 20px;
    transition: var(--transition);
}

.faq-question span {
    font-family: var(--font-cn);
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--color-black);
    line-height: 1.4;
}

.faq-icon {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: var(--color-bg-light);
    border: 1px solid var(--color-border);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    transition: var(--transition);
    color: var(--color-black);
    font-size: 0.9rem;
}

.faq-item.open .faq-icon {
    background: linear-gradient(135deg, var(--color-brand-dark) 0%, var(--color-brand) 100%);
    color: var(--color-white);
    border-color: transparent;
    transform: rotate(45deg);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.45s cubic-bezier(0.16, 1, 0.3, 1), padding 0.3s ease;
}

.faq-answer p {
    font-size: 1rem;
    color: var(--color-grey-dark);
    line-height: 1.8;
    padding-bottom: 28px;
}

.faq-item.open .faq-answer {
    max-height: 300px;
}

/* === Responsive Design === */
@media (max-width: 1200px) {
    .hero h1 { font-size: 4rem; }
    .overview-grid, .platform-grid { gap: 60px; }
}

@media (max-width: 1024px) {
    .hero h1 { font-size: 3.5rem; }
    .overview-content h2, .platform-content h2 { font-size: 2.5rem; }
    .data-card { padding: 24px; left: -20px; }
    .data-card h3 { font-size: 2.4rem; }
    .features-grid { grid-template-columns: repeat(2, 1fr); }
    .banner-text h2 { font-size: 2.4rem; }
    .faq-layout { gap: 60px; }
    .faq-left h2 { font-size: 2.4rem; }
}

@media (max-width: 768px) {
    /* Hide desktop nav items; keep lang dropdown visible (globe icon only) */
    .nav-menu, .nav-right .btn-header { display: none; }
    .mobile-menu-btn { display: block; }

    /* Compact lang toggle on mobile: hide text label and chevron */
    .lang-toggle .lang-current-text,
    .lang-arrow { display: none; }

    /* Align lang dropdown to right edge on mobile */
    .lang-menu { right: 0; left: auto; }

    .nav-menu.active {
        display: flex;
        flex-direction: column;
        position: absolute;
        top: 100%; left: 0; width: 100%;
        background: var(--color-white);
        padding: 20px 24px;
        box-shadow: 0 20px 40px rgba(0,0,0,0.1);
        border-top: 1px solid var(--color-border);
        gap: 0;
    }
    .nav-menu.active a {
        color: var(--color-black);
        padding: 14px 0;
        border-bottom: 1px solid var(--color-bg-light);
        font-size: 1rem;
        letter-spacing: 0;
    }
    .nav-menu.active a:last-child { border-bottom: none; }
    .nav-menu.active a.active {
        color: var(--color-black);
        font-weight: 700;
    }
    .nav-menu.active a.active::after { display: none; }

    .section-pd { padding: 80px 0; }

    .hero { min-height: 640px; }
    .hero h1 { font-size: 2.8rem; }
    .hero-arrow { display: none; }
    .hero p { font-size: 1.05rem; }

    .overview-grid, .platform-grid { grid-template-columns: 1fr; gap: 48px; }
    .image-composition { margin-bottom: 20px; padding-right: 0; }
    .img-main { width: 100%; }
    .img-sub { width: 60%; right: 0; }

    .features-grid { grid-template-columns: 1fr; }
    .feature-card { padding: 36px 28px; }

    /* iOS Safari: fixed background-attachment is broken */
    .banner-cta { background-attachment: scroll; }
    .banner-container { flex-direction: column; text-align: center; gap: 40px; }
    .banner-text h2 { font-size: 2rem; }

    .footer-grid { grid-template-columns: 1fr 1fr; gap: 40px; }
    .platform-images { height: 400px; order: -1; }
    .platform-item { padding: 0; }
    .platform-item:hover { background: transparent; border-color: transparent; }

    .stats-grid { grid-template-columns: repeat(2, 1fr); }
    .stat-item { border-right: none; border-bottom: 1px solid rgba(255,255,255,0.08); }
    .stat-item:nth-child(odd) { border-right: 1px solid rgba(255,255,255,0.08); }
    .stat-item:nth-last-child(-n+2) { border-bottom: none; }

    .steps-grid { grid-template-columns: 1fr; }
    .steps-grid::before { display: none; }

    .faq-layout { grid-template-columns: 1fr; gap: 40px; }
    .faq-left h2 { font-size: 2.2rem; }
}

@media (max-width: 480px) {
    .container { padding: 0 20px; }
    .section-pd { padding: 60px 0; }
    .hero h1 { font-size: 2.2rem; }
    .hero p { font-size: 1rem; margin-bottom: 36px; }
    .footer-grid { grid-template-columns: 1fr; }
    .footer-bottom { flex-direction: column; gap: 24px; text-align: center; }
    .overview-actions { flex-direction: column; align-items: flex-start; }
    .data-card { position: relative; top: 0; left: 0; margin-top: -40px; width: 90%; margin-left: 5%; }
    .stat-item .stat-num { font-size: 2.2rem; }
    .platform-images { height: 300px; }
    .feature-card { padding: 28px 22px; }
}