:root[data-theme="dark"] {
    --bg-image: url('./assets/aurora_dark.png');
    --text-primary: #ffffff;
    --text-secondary: #cbd5e1;
    --glass-bg: rgba(15, 23, 42, 0.4);
    --glass-border: rgba(255, 255, 255, 0.1);
    --glass-shadow: rgba(0, 0, 0, 0.3);
    --accent: #2dd4bf; /* Teal/Cyan */
    --accent-hover: #14b8a6;
}

:root[data-theme="light"] {
    --bg-image: url('./assets/aurora_light.png');
    --text-primary: #1e293b;
    --text-secondary: #334155;
    --glass-bg: rgba(255, 255, 255, 0.5);
    --glass-border: rgba(255, 255, 255, 0.6);
    --glass-shadow: rgba(100, 116, 133, 0.15);
    --accent: #0284c7; /* Ocean Blue */
    --accent-hover: #0369a1;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Outfit', sans-serif;
    transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease;
}

html {
    scroll-behavior: smooth;
}

.background-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    z-index: -1;
    background-image: var(--bg-image);
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
    transition: background-image 0.8s ease-in-out;
}

body {
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    overflow-x: hidden;
}

/* Glassmorphism Utilities */
.header-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 5%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
}

.glass-panel {
    background: var(--glass-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--glass-border);
    box-shadow: 0 8px 32px 0 var(--glass-shadow);
}

/* Header & Nav */
header {
    position: sticky;
    top: 0;
    z-index: 1000;
    padding: 15px 0;
    border-top: none;
    border-left: none;
    border-right: none;
    border-radius: 0;
}

.logo-link {
    display: inline-block;
    height: 60px;
    transition: transform 0.3s ease;
}

.logo-link:hover {
    transform: scale(1.05) translateY(-2px);
}

.logo-img {
    height: 100%;
    width: auto;
    object-fit: contain;
}

/* Dark mode logo inversion */
:root[data-theme="dark"] .logo-img {
    filter: invert(1);
}

:root[data-theme="light"] .logo-img {
    filter: invert(0);
}

.main-nav {
    display: flex;
    gap: 3rem;
}

.main-nav a {
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 500;
    font-size: 1.05rem;
    position: relative;
    padding: 0.5rem 0;
    transition: color 0.3s ease;
}

.main-nav a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--accent);
    transition: width 0.3s ease;
}

.main-nav a:hover {
    color: var(--accent);
}

.main-nav a:hover::after {
    width: 100%;
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

/* Buttons */
.btn-primary, .cta-btn {
    background-color: var(--accent);
    color: #fff;
    padding: 0.8rem 2rem;
    border-radius: 50px;
    text-decoration: none;
    font-weight: 600;
    font-size: 1.1rem;
    transition: background-color 0.3s ease, transform 0.2s ease;
    display: inline-block;
    border: none;
    cursor: pointer;
}

.btn-primary:hover, .cta-btn:hover {
    background-color: var(--accent-hover);
    transform: translateY(-2px);
}

.icon-btn {
    background: transparent;
    border: none;
    color: var(--text-primary);
    font-size: 1.3rem;
    cursor: pointer;
    transition: transform 0.2s ease;
}

.icon-btn svg {
    width: 1.3em;
    height: 1.3em;
    stroke-width: 2;
}

.icon-btn:hover {
    transform: scale(1.1);
}

/* Hero Section */
.hero {
    display: flex;
    justify-content: center;
    align-items: center;
    width: 100%;
    padding: 2rem 0;
}

.hero-content {
    text-align: center;
    padding: 4rem 3rem;
    border-radius: 20px;
    max-width: 1000px;
}

.hero-content h1 {
    font-size: 4rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
}

.hero-content p {
    font-size: 1.1rem;
    line-height: 1.6;
    color: var(--text-secondary);
    margin-bottom: 2.5rem;
    padding: 0 1rem;
}

.hero-cta {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

.hero-cta .subtitle {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin: 0;
    padding: 0;
}

/* Sections Base */
main {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 2rem 5%;
    gap: 6rem;
}

.features-wrapper {
    width: 100%;
    max-width: 1300px;
}

.features-container {
    padding: 5rem 4rem;
    border-radius: 32px;
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.features-container .section-title {
    font-size: 2.8rem;
    color: var(--accent);
    margin-bottom: 4rem;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
    width: 100%;
    max-width: 1200px;
}

.feature-item {
    text-align: left;
    padding: 2.5rem 2rem;
    border-radius: 20px;
    transition: transform 0.3s ease;
}

.feature-item:hover {
    transform: translateY(-5px);
}

.feature-item .feature-icon {
    font-size: 2rem;
    color: var(--accent);
    margin-bottom: 1.5rem;
}

.feature-item .feature-icon svg {
    width: 1.5em;
    height: 1.5em;
    stroke-width: 2;
}

.feature-item h3 {
    margin-bottom: 1rem;
    font-size: 1.4rem;
    font-weight: 600;
}

.feature-item p {
    color: var(--text-secondary);
    font-size: 1rem;
    line-height: 1.7;
}

.features-section {
    width: 100%;
    max-width: 1100px;
    display: flex;
    flex-direction: column;
    gap: 8rem;
    padding: 6rem 0 2rem;
}

.feature-split-block {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 4rem;
    width: 100%;
}

.feature-split-block.reverse {
    flex-direction: row-reverse;
}

.feature-split-text {
    flex: 1;
    text-align: left;
}

.feature-split-text h2 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.feature-split-text .zh-subtitle {
    font-size: 1.5rem;
    font-weight: 600;
    font-style: italic;
    margin-bottom: 2rem;
    color: var(--text-secondary);
}

.feature-split-text p {
    font-size: 1.15rem;
    line-height: 1.8;
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

.feature-split-text p.zh-text {
    font-size: 1rem;
    font-style: italic;
    margin-top: 1rem;
}

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

.feature-split-image img {
    width: 100%;
    max-width: 500px;
    height: auto;
    border-radius: 24px;
    box-shadow: 0 20px 50px rgba(0, 0, 0, 0.4);
    object-fit: cover;
    transition: transform 0.4s ease;
}

.feature-split-block:hover .feature-split-image img {
    transform: translateY(-8px);
}

/* FAQ Section */
.faq-section {
    width: 100%;
    max-width: 900px;
}

.faq-container {
    padding: 5rem 4rem;
    border-radius: 32px;
    text-align: center;
}

.faq-container h2 {
    font-size: 2.5rem;
    margin-bottom: 3.5rem;
    color: var(--accent);
}

.faq-list {
    text-align: left;
    display: flex;
    flex-direction: column;
    gap: 1.2rem;
}

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

.faq-question {
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 0.5rem;
    background: transparent;
    border: none;
    color: var(--text-primary);
    font-size: 1.15rem;
    font-weight: 600;
    cursor: pointer;
    text-align: left;
    transition: color 0.3s;
}

.faq-question:hover {
    color: var(--accent);
}

.faq-question svg {
    width: 1em;
    height: 1em;
    transition: transform 0.4s ease;
}

.faq-item.active .faq-question svg {
    transform: rotate(180deg);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s cubic-bezier(0, 1, 0, 1);
}

.faq-item.active .faq-answer {
    max-height: 500px;
    transition: max-height 0.6s ease-in-out;
}

.faq-answer p {
    padding: 0 0.5rem 1.5rem;
    color: var(--text-secondary);
    line-height: 1.8;
    font-size: 1.05rem;
}

/* About Brand (Bottom story) */
.about-brand {
    width: 100%;
    max-width: 1100px;
    margin-bottom: 6rem;
}

.about-brand .about-container {
    padding: 6rem 4rem;
    text-align: center;
    border-radius: 32px;
}

.about-brand h2 {
    font-size: 2.8rem;
    margin-bottom: 3rem;
    color: var(--accent);
}

.about-story {
    max-width: 800px;
    margin: 0 auto;
}

.about-story p {
    font-size: 1.25rem;
    line-height: 1.9;
    color: var(--text-secondary);
    margin-bottom: 2.5rem;
    text-align: left;
}

.about-story p:last-child {
    text-align: center;
    color: var(--accent);
    font-style: italic;
    font-weight: 600;
    font-size: 1.4rem;
    margin-top: 4rem;
}

/* Responsive */
@media (max-width: 1024px) {
    .main-nav {
        gap: 1.5rem;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
        gap: 3rem;
    }
    
    .feature-split-block,
    .feature-split-block.reverse {
        flex-direction: column;
        gap: 3rem;
        text-align: center;
    }
    
    .feature-split-text {
        text-align: center;
    }
}

@media (max-width: 768px) {
    .main-nav {
        display: none; /* Hide for mobile focus on simple header or add burger later */
    }

    .header-container {
        flex-direction: row;
        justify-content: space-between;
    }

    .features-container,
    .faq-container,
    .about-brand .about-container {
        padding: 3rem 1.5rem;
    }

    .about-brand h2 {
        font-size: 2rem;
    }

    footer {
        flex-direction: column;
        gap: 1.5rem;
        text-align: center;
    }
}

/* Footer */
footer {
    width: 100%;
    background: var(--glass-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-top: 1px solid var(--glass-border);
    padding: 2rem 5%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    color: var(--text-secondary);
}

.footer-links {
    display: flex;
    gap: 2.5rem;
}

.footer-links a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: color 0.3s ease;
    font-size: 0.95rem;
}

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